What year 235? And is it mandatory in your mind to have a manual choke or are you willing to accept an automatic choke? Carter YF models are very good...however they were carefully engineered to recognize changes in the 235's design. Rochester carburetors make good paperweights or doorstops and if you fish in a lake they're also good to weigh down trot lines. You can also throw them at gophers, moles, etc. They can be handy for that or they can be used as a wheel chock if you must park on a hill.
Like the other Jon, I'd begin with a compression test. I'd follow that with a check of ignition timing and a check of the vacuum advance unit. Backfiring might not be the fault of your carburetor...or it might. Two things commonly cause this. One is early ignition timing and another is an exhaust valve not opening or not opening correctly or a sticky valve. I've also seen this happen due to cross-firing of plug wires, a bad distributor cap (one with carbon deposits that allow a cylinder to fire when it isn't supposed to) and it can be caused by a bad accelerator pump or plugged passage. The pump tries to squirt gas in when the accelerator is pushed down but it doesn't succeed. The engine goes really lean because it gets more air than it needs and it backfires.
