Fast68,
Unhook the pcv line from the carb, plug the port.
Try it again.
ok, maybe too much vacuum?

Power brakes? Could be a leaky diaphragm.
yes, I’ll check

If it has really weak springs in the distributor, it might just have so much timing it’s keeping the rpm up.
I’ll see what’s in it

TJP,
Have you tried driving it without the air cleaner ?
yes, no change.

Also make sure there is a bit of slack in the accelerator cable when idling warm off choke
there is

Speaking of chokes, any chance the fast idle cam is activating??
I’ll check

Stumpy,
Might want to check out the motor mounts to be sure the motor isn't torqueing over putting things in a bind.
should have bound while still in park though, right?