Did you get your existing carburetor rebuilt or did you get a carburetor from a box from a parts store (and yes, it makes a big difference).
Was the original carburetor leaking fuel externally or internally (into the engine)?
If externally, where about was it leaking from?
Anytime a carburetor is replaced, rebuilt or repaired, one always needs to adjust the idle mixture, idle speeds and so on.
Also check all vacuum hoses (for disconnection and for cracks). Many times I have seen a seemingly good appearing vacuum hose, split on bottom side close to its fitting. Also, check the brake booster for leaks (it should have enough vacuum inside of it for one and one half power assisted stops with engine off - after engine has been off for a good length of time).
The intake gasket can be checked for leaks by spraying canned parts cleaner around the intake to cyl head with engine running. If engine speeds up (or slows down) just after spraying an area - usually is a good sign of a gasket leak.
A hand held vacuum pump can check for leaks at the distributor vacuum advance or carburetor choke pull off. If you don't have one, sometimes one can be rented from your local parts store.
BudW