a regular ticking fluctuation on the vaccum gauge could mean just that the valves need to be adjusted. Might start with that. I.E. one valve is not closing all the way. A quick check with compression testor might show which cylinder.

I am assuming that you have the timing set to to stock and the motor is stock.

You can check the vaccum advance on the distributor by putting a vaccum pump on it and then watching the timing light.

\'59 Chevy 1-ton
'72 c-10 (in progress)
The Great Rust(less) Mountain
\'47 Jeep cj2a