No spark at plugs. Test light will light at the wire going into the dist. Also will light at small piece of points. Sometimes I get spark at wire coming out of magnito. Not sure if it was a good ground when I tried it.

The ignition coil will have two small nuts , one on each side of the spark plug wire. It can be labeled many ways, + - , pos neg , Bat Dist , point will hook to the - ,NEG , Dist . The only time this will be the other way is when you system is a Positive ground, that is the + , positive of the battery hooked to the frame instead of the - Neg.

That truck should have no points. It should have electronic ignition. Sounds like bad wires or bad coil(s).

It could be, but anybody with a multimeter could quickly test it, give you a good idea if it is good or not. Just take the two wires off-the wire going to the distributor would be the negative side, and the wire from ignition switch is the positive side. There should be a + sign, and a - sign on each side of the coil case where the wires connect. Then remove the coil to distributor high tension cable, remove the coil from it's bracket and take it to a friend or shop to have tested. All they would do is measure the resistance of the coil at two places, using an ohmmeter (part of a multimeter), to see if it is within specs. A shop charge should be like $5, if they would even bother to charge you.
What else might it be? Well, one could check if power is passing from the switch to the coil on that wire. The wire on the coil should show battery voltage, or very close, when key is turned to on. Also examine your plug wires for brittleness or cracking. If no spark at any plug, it could be a bad coil to distributor high tension lead-the one from coil tower to center of distributor cap.
Also pertinent to note that the mechanical points and condensor assembly inside the distributor has to be working right for spark to occur. This is what the small wire from coil to distributor connects to- the points. Someone knowledgeable about how it works would need to look at it-the points have two small electrical plates or contacts that open and close as the distributor shaft turns around. This opening and closing is what makes the coil able to generate the high voltage for spark to occur at the plugs. Higher voltage travels from the coil tower to the top of distributor, and on to the individual spark plug wires, routed to each in turn in the firing order by a simple device called a rotor.
Take off the distributor cap, and right on the top of the distributor shaft is the rotor. It has to be in good working order to transfer current from the coil high tension wire to the individual spark plug wires.
Post back. Keep me informed of your progress. You must have the old 6 volt system? Amazing! Buy new plugs, plug wires, points and condensor for it. And a coil, if you need to-good luck. Parts may be hard to find. First check locally, may need to go online for a vintage parts supplier.

Test the primary side of the coil. Disconnect the small wires from both ends of the coil. Then, use a digital volt ohm meter to test the resistance of the coil. Put the meter's function switch in OHMS, R X 1 scale. Touch one meter probe to each one of the terminals on the ends of the coil. The meter should read between 5-6 ohms of resistance. If it does this, reconnect the white wire to the top terminal of the coil. Take a plain piece of wire and strip about an inch of insulation from each end. Connect one end of this wire to the bottom terminal of the coil. Put both spark plug wires in the coil with a spark plug in each wire. Make sure the plugs are grounded to the engine. Turn the ignition switch on and MOMENTARILY touch the wire you connected to the bottom terminal of the coil to the engine and then take it away from the engine. When you take the wire away from the engine ground, you should see a spark at both plugs. If not, the coil is bad. Have you cleaned and checked the gap on your points? Clean the points using a thin piece of stiff paper like a piece of index card with a bit of alcohol on it. Set the gap on the points to 0.020". Make sure the gray wire from the points is connected to the bottom terminal of the coil.

Good Luck
Steve

Sounds like wet or moist spark plug wires. If this also occurs during early morning high dew point humid air, then you may have spark plug wires shorting out.

Replace wires.

GET A PIECE PAPER DRAW A LARGE CIRCLE TOP UPPER HALF CIRCLE LEFT TO RIGHT WRITE NUMBERS 1 AND 3 BOTTOM HALF CIRCLE LEFT TO RIGHT RIGHT NUMBERS 2 AND 4 THAT YOUR DISTRIBUTOR SPARK PLUGS WIRES LOCATION.STANDING ON SIDE OF ENGINE WHERE DISTRIBUTOR IS LOOKING DOWN AT DISTRIBUTOR 1 AND 3 FIRST TWO SPARK PLUGS TERMINALS NEXT TO ENGINE. AND 2 AND 4 SPARK PLUGS TERMINAL ON CAP FACING YOU. THIS IS CYLINDERS LOCATIONS STANDING IN FRONT OF ENGINE.RUN WIRES FROM DISTRIBUTOR CAP TO PLUGS TO THE ENGINE SPARK PLUGS.

This sounds like ignition wires if they are cracked and chaped this will cause hard start if at all .Want to test them?at night open hood you might see sparks if you want spray a bit of water from a spray bottle lightly once you wil see small sparks.

with # 1 piston (front piston on drivers side) on tdc compression stroke place distributor in pointing at the front of the drivers front tire as it drops in it should point roughly at the # 1 piston as it rotates clockwise as it drops in , the cam gears have to mesh so dont force it . if it wont drop into place try a small bump of the starter while applying light pressure down on the dist.it should drop into place and then lock it down a bit . get #1 piston back on tdc compression stroke make sure the power wire is off the dist . the big red 1..you dont want it having spark yet. if it goes into place then set your cap and wires back in and time it with timing light .remove vacum hose from vacum can on side of dist and plug the hose off then use timing light and set to what factory says , usually between 4-8 degrees btdc. 1-3-5-7 piston numbers front to back drivers side ///// 2-4-6-8 front to back on pass side firing order is 1-8-4-3-6-5-7-2 and the dist should have #1 pointing at the drivers front corner of engine. start # 1 plug wire there and work clockwise next spot clockwise on dist is #8 plug wire and so on.. good luck

Check for power getting to the center top connection at the coil.
Are the points opening?
Are they fully closing?
Check for a grounded connection/wire in the dist?
Be very careful how you set the coil onto the dist.

If you have a 12 volt test light put the point on the positive lead to
the coil and the ground lead to a good ground ( Negitive side of battery ). Then turn the key on. If the test light comes on then you have power to the coil. With power to the coil confirmed have someone crank the engine and put the test light on the negitive side of the coil. The light should flash at a rapid steady rate. If not then your pickup in the distributor may be bad. If no power to coil with key on or when cranking you may have a bad ignition switch.
Another way to test for spark is to remove the coil wire from the dist cap and hold the end close to a ground ( 1/4 inch away) and
have some one crank the engine. If you get a good spark but no
spark to the spark plugs you may have a cracked dist cap or a bad rotor. If no spark at coil wire use a wire in place of the coil wire to check for spark. You may have a bad coil wire. Good luck. Neil W.