First thing to do is to determine if it is lacking ignition fire or fuel. If the compression is good those are the only other things it needs to run. You can try a spray can of starting fluid into the carb while cranking the starter, if that makes it run you know it is a fuel issue. If not, then remove a couple of plugs and lay them on the motor so they have a ground path and with the wires connected crank it over and watch for good hot spark at the plugs. If it has good hot fire, the ignition system checks ok. If you don't find anything there, I will need to know which motor, 4.3L or something else. I will also need to know what kind of ignition system it is running (HEI? external coil and module?) and what you have tried already. Does it use a crank and cam sensor? Have you rechecked the firing order, to be sure? Have you checked the base ignition timing? Have you checked the fuel to be sure it is not contaminated? Basics first and then go from there. If nothing else, run a compression test to be sure you do not have any internal problems with it, like a timing chain, etc. Let me know. Thanks
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