Engine specs?
Carburetor number?
How much timing at idle?
Check to make sure the throttle plates are all fully closed and well sealed up. Very common problem after bushing installation to not get the plates well "indexed" and have some unwanted air getting by them, or sticking a bit when they close and letting in enough air to have the engine idling too fast.
Timing is another big issue, weak distributor springs, installing one of those aftermarket kits into the distributor, running manifold vacuum to the advance and having too much timing at idle speed, etc......Cliff