There have been a number of threads about the replacement Chinese carburetors. While not a single barrel, here is an in-depth analysis of one of the Chinese knock-off Rochester Q-Jets by one of the most respected of all Q-Jet specialists:

Chinese Q-Jets

Those who believe in the tooth fairy, Santa Claus, or the cheap Chinese carburetors should read this article in its entirety!

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop