Guys, don't spend too much on these Rochester carbs. Brian Gough and I passed the $15.00 ones by at Hershey because there were lots there cheaper. Look for the ones with the manual choke brackets still in place. These carbs are really trouble free and in 40 years of working on them I have never had a problem that wasn't easily fixed. Usually it was my fault anyway!
Kits are about 15 to 20 bucks, Just make sure the passages are clean. To obtain proper performance you should use the proper size carb on the 261. Also it is better to use the exhaust manifold also, even though most most of them exit at an angle and you need a bigger exhaust pipe. You probably need the pipe made up anyway. Also make sure the heat riser functions. When we used to have a lot of these engines coming in for tune ups we always checked the manifold to head nuts and gave each one a little tweak.
Cheers,
Barry