Replaced head set time with marks also by checking when vaules oped and it is in time the only way it will crank is hold the throttle wide open and it skips runs badly

Is the truck a E85 flex fuel vehicle? Not wanting to start sometimes until you give it wide open throttle means it's getting too much fuel, wide open throttle cuts fuel injectors fuel delivery.
Clear Flood Mode
If the engine floods, clear the engine by pressing the accelerator pedal down to the floor and then crank the engine. When the TP sensor is at wide open throttle (WOT), the ECM reduces the fuel injector pulse width in order to increase the air to fuel ratio. The ECM holds this injector rate as long as the throttle stays wide open, and the engine speed is below a predetermined RPM. If the throttle is not held wide open, the ECM returns to the starting mode.

Do you have a scan tool that can look at live data, fuel trims? Is the ECM adding fuel or taking fuel away. Mass air flow sensor data etc... Flex fuel calibrations may need to be reset .

P0172, P0300, Extended Crank-Incorrect Alcohol Content-Flex Fuel System - YouTube

You said no codes, that doesn't matter

remove the plug, hold the throttle wide open and pull about 10 times
replace the plug and hold the throttle wide open, pull to start
the stihl floods very easy and will not start until the excess in the crankcase is removed

I would do a compression test of the engine. Spend about $40 for the gauge tester and do it yourself. Engine should be at operating temperature, remove all spark plugs, disable ignition by grounding the high tension cable from coil to distributor, screw in the gauge to one cylinder, hold the gas pedal to the floor-or hold the throttle at wide open, then crank engine for about 5 seconds. You will have a compression reading that should be somewhere between 100 psi and 200 psi. Anything below 100psi means not enough compression in the cylinder to produce power when running. Do each cylinder the same-crank the same amount of time for each cylinder( with wide open throttle). All compression readings should be fairly close-lowest reading must be within 75% of highest reading cylinder for a good, healthy engine.

If compression is low in any cylinder, it probably won't even fire the air/fuel mixture. Look for valve problems, valves not sealing (burnt valves cause this), or piston rings worn too bad, head gasket failure can cause low compression. Example, compression tested a Nissan, and readings were all 155-160 psi in all cylinders, so compression was excellent, engine was internally good. If you have good compression in each cylinder, look elsewhere like a plugged catalytic converter-won't let the engine breathe, or a problem with the ignition system-test for a snapping, blue spark when cranking the engine, on one of the spark plug wires. Others: check EGR valve for being stuck open, good luck, then.

you need to check all sensor connections as the crank shaft sensor also will mess up your idle....try slightly unscrewing the tps and push it up or down slightly to see if this fixes the problem.

i think you may have not put the timing right if you have changed the head gasket or removed the timing, make sure all timing is lined up on timing marks cams and the crank. adjust till they line up using piston number one as top dead. turn engine by hand (spanner on crank) and make sure they line up each time it goes to top dead on number 1.

take the head off bent valves thats for sure

no your problem is not the heads you have it right timing is off try putting it on time again you will get it to start and run right,you might be off by 180 degrees try spinnig distributor 1/2 turn and drop back down.always ssstart with the crank on tdc.

u may have an intake manifold leak or low cylynder pressure

first check to be sure the vavuum lines at the throttle body are in there correct places.
on the main pulley of your engine, the one on the crank shaft there will be a little notch on it. mark the notch with some chalk or a dab of white paint. then loosen the bolt that holds down the distributor until you can turn the distributor. turn the distributor a little bit, snug the bolt up and try it. once you have the car running you will need a timing lite to set the timing to the correct timing mark. which should be 8 degrees before top dead center for you car.