Easy to check for definitely bad.

Using an ohmeter, check from + to - on the coil. Depending on the coil it should read between .5 ohms and 4 ohms. If not it is defective.

Then check from - to the metal in the bottom of the socket where the high voltage lead plugs in. Depending on the coil it should read between 5000 ohms and 30000 ohms. If not it is defective.

Anything else has at least a chance of being good and could only be tested by either trying it on the truck/car or by using expensive test equipment.
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'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.