I'd start by blocking off all vacuum lines at the carb, check your dwell (if you're running points), check your timing; if these are within spec set your carb to the idle you want (typically no higher than 750 rpms), reconnect all lines and see how the car performs.
Vacuum wiper pumps are nortorious leakers; this is worth checking. If your wipers work well the pump probably isn't leaking.
The duration of the Cam Shaft also affects vacuum and idle. You may have to run the carb at a higher idle to stabilize the vacuum or add a vacuum reservoir. If you're running an automatic trans you don't want to turn the idle up so high that it bangs into gear (this will cause the front pump to fail prematurely). If you're running a 350 or a 400 turbo check the modulator valve line and valve to insure there are no leaks.
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