Ol RustyCranks 74 Dart

Ive got a question that ive been pondering on that maybe yall know. Does anyone know the the difference between the rocker measurements on a /6 and LA small block? Reason I ask is that manual rocker arms, even cast iron are few and far between around my area. I was thinking if they are close (bolt spacing, rocker geometry) cut it short and put a plug in the end and viola cheap manual rocker arms. What do yall think?