Idle high

You havent posted your idle vacuum reading yet. Nor answered the question about vacuum advance hook up.
Make sure the vacuum advance isntworking at idle.How about throttle cable adjustment? Vacuum lines can be pinched off, one at a time.
Your combo should easily idle down to 850ish,and make near 11 inches vacuum, with your current mechanical idle-timing of 19*.
I suppose you took the intake off to replace the lifters, right? Was the carb removed from the manifold?Did the carb receive any adjustments other than idle speed, between cams?Any chance the gasket(s) got tweaked during the manifold re-install?
Just for curiosity sake; what did it idle at with the old cam and what were the cam specs of that old one?

A vacuum canister is a vacuum storage device. It stores vacuum created during times when the engine is making high vacuum, for use by vacuum operated devices ,later, during times of low vacuum.It does it automatically.It also acts to smooth out any vacuum pulses. It is most often used to help the power brakes function at stoplights when a big-cam engine is idling and not making enough vacuum. Other devices that can benefit are; A/C controls, certain emission devices/timing controls,vacuum headlamps,and pretty much anything that depends on a constant source of vacuum to operate.
It could be used to kick your vacuum advance in at idle,but theres not much benefit in doing that on your combo.Your cam should make enough vacuum to power the booster.I had a 292/509 that was no problem.