First, welcome to Club Hot Rod! It's good to see you here.

I'd say let's start with some basics, Have you completed a compression check? Pull all the plugs, disconnect the power from the ignition, hold the carb ( if equipped) or throttle body wide open and insert a compression gauge in place of a spark plug, spin it with the starter and count 3 strokes, record the readings and let us know the findings.

It's going to be these basic tests, like compression checks and vacuum readings that will tell you the health of the motor.