18 spline A body 4 speed

Back in the 70's we would put built 440's in 383 23 spline 4 spd b-body cars . The brass forks were the only weak link on a "no lift shift" if you didn't get it all the way in it would get forced back out and break the fork. 3-4 was the usual fork I broke, I always liked the close ratio gearing on the 71 and newer trans. And the steel forks. Having the correct rear gear helps with that close ratio trans