350ci gm motor, mallory unilite distributor, flamethrower coil. question: should stock ceramic 75ohm ignition resistor be used with this combination?

It would be the pickup in the bottom of the distributor.

The wiring of an ignition coil is fairly straightforward as there is only two terminals and regardless of whether there is an electronic distributor or the old fashioned contact breakers, in the basic 12 volt ignition system the wire from the ignition switch is connected to the + or Batt terminal of the coil and the single wire from the distributor connected to the - or CB terminal.

That system became quite rare over time as the ballasted system performed much better for little more cost. The primary resistance of the 12 volt coil is around 3 ohms and the ballast type around 1.5 ohms. It is important the correct coil is used.
You mentioned resistor so it is reasonable to assume it is a ballasted system. In this system one of three types of resistor is used - while many used a length of resistance wire integrated into the wiring harness the AC Delco system used a carbon "pill" type resistor mounted directly on the + coil terminal.
The third type is probably the best and is a ceramic unit with resistance wire inside, usually bracketed on the coil bracket or nearby.

The ballasted system uses a low resistance coil. One end of the resistor is supplied from the ignition switch and the other end is connected to the coil + terminal. There is a third wire directly from the starter solenoid also connected to the + terminal so when the ignition key is turned to crank the engine, battery voltage is supplied to the coil bypassing the resistor and producing a much more powerful spark making starting easier.

By 1986 many vehicles had begun to use either integrated distributors (with the amplifier inside) or a discrete amplifier mounted near the coil. The connections to these is fairly intuitive as multiway connectors take care of most of the wiring though the coil wiring remained basically the same on the + side.

is the mallory an hei dist there is a plug on the side of the cap 1 says batt 1 says tach

check firing order and ignition timing. Ensure that you have connected the distributor up correctly to the coil. Check to see if the unit requires tacho (rpm gauge) wires connected. Some of these units need the rpm's reading as the ignition pulse determines the advance of the spark

What size engine? What is the credit card trick, never heard of that one before. Does this car have a knock sensor? Crank sensor?

the coil doesn't need a ballast resister how ever the module in the distributor does found that the hard way many miles from home

Without any more information than this I have to say it should be between 32 and 35 thousands. I don't have the info from the ignition system that your using, Have you checked the manufactures suggestions. Unless this is a super spark ignition then the gap I quoted should work.

Try a hot wire to the distributor. If the engine keeps running then the problem may lie with the ignition circuit wiring. It also might be the ceramic resistor.

you can find that information in your local chiltons manual or you local parts store

i don't beleve 3 volt is enaf for the coil it has to be at least 9 volts
if this car has a resistor on the car or on the circuit going from ignition switch to ignition coil replace it, but if it does not have one then it has to have one built in the circuit wish is going to be very hard to find i will recomed you to get straight ignition power from ignition sw, to an aftermarket ignition resistor and from there to the positive side of ignition coil,
but also let me know what promaster means? is that the brand? or is that a performance coil?
and does your car has elecgtronic? or points system ignition distribuitor.