There is also a Carter YF4145S that was used on the Chevrolet 194, 230 and 250 engine as well as the YF3821S or YF3821SA. Both of those have a manual choke and I tried a 4145S on a 235 once upon a time. It worked ok but the throttle rod connection was on the wrong side (I had to make an adapter which wasn't difficult at all) and it seemed to run slightly rich on the 235 so that one might be ok on the 261. Those were much cheaper than some of the YF carburetors out there. I have seen some of them on the big auction site for $50 or less. They'd need rebuilding but almost anything you get will need that.
