Timing

just wondering, do you have solid or hydraulic lifters?

Since you have issues with bouncing vacuum, have you checked for any vacuum leaks? I swapped my intake manifold a few weeks ago and I couldn't get my idle below 1000 RPM. Vacuum signal was steady but I still had a huge vacuum leak.

The fact that your vacuum is still bouncing might indicate you have a leak somewhere (unless you have a radical cam in there) messing with the way your engine runs. Try spraying some water around the intake manifold and carburetor to see if the engine rpm's change. If they do this indicates you have a vacuum leak.