Help - idle speed too fast

[scumdog]

Ok, the carb on my '66 'bird had it idling too fast so I took it off and put a 780 Holley on, it didn't make it runn as well as I wanted so put the original carb on.

Now it idles even faster!!

I checked for:
Throttle linkage sticking - it's not.
Vacumm leak - disconnecting and plugging the lines made no difference.
Choke - adjusted it so the flap was straight up and down
Hold-down studs - the nuts are all snugged down
Dash-pot - adjusted it so it's not making contact

So any other ideas???????