Somebody else will chime in who has more experience with 6 volt systems, but here is how it is done with 12 volt negative ground systems.
A hot wire (Positive +)from the ignition switch goes to the "+" side of the ignition coil. Another wire goes from the "-" side of the coil to the distributor. This might be switched if you have a positive ground system. If your truck is a Canadian GMC with a 216 motor, it should be Negative ground.
The spark should be seen when the engine is cranked, the ignition is on, and the spark plug is grounded to something, weather that is the engine block or the frame, or the inner fender it doesn't matter. If you see a good strong spark, your ignition is good. The spark should be equally bright on the frame or the engine. If not, the engine needs to be properly grounded.
Since your truck has been sitting for almost 20 years...A COMPRESSION TEST IS NECESSARY! It is very likely you have 1 or more stuck valves and bent pushrods.
I'm not sure what a 216 should read on a compression guage, but it is probably somewhere between 125 and 170 psi. If you have compression of 90 psi or better in each cylinder, the engine should start. If you are looking at numbers in the 30 psi range, it is very likely that you have rusted rings, stuck valves, or both.
Please beg, borrow, or steal a compression tester and get back to us.
John
