I'm not positive about the years, but after Chevrolet quit putting the hand crank fitting on the balancer, the balancers had a nearly-square hole that would accept a 3/4" square drive breaker bar or ratchet. These could slip in between the radiator and the balancer, and it made it quite easy to turn an engine. I still have the balancer with that fitting that came on my 1953 235. I recall using the method on several engines when I was working as a mechanic in the fifties and sixties. I just went out to my shop and looked at the balancers on two later 261s (post 1958s) and they do not have the square hole. The last time that I built a 261 in 2006 I tapped the crankshaft snout for an ARP 1-1/8" cap screw. This makes it easy to rotate the engine, with all of the spark plugs in and 11:1 compression. I also used to use a scissors screw jack handle to rotate my 1948 216 back in 1955.
Hoyt
