I've looked in several books but can't seem to answer this, since 86 up small blocks are externally balanced are the cranks the same{305/350}. I know the pre 86 sbc 305 and 350 had different counter weights for balance but they were internally balanced.

 

common mistake but all SBC cranks are internally ballenced with the exception of the 400. when gm went to the 1 piece main seal they lost the mass of the flywheel flange so to make up for this loss they went to the dowel pinned flywheel and the bat wing weight. the 305 and 350 cranks aren't balanced the same since they have very differant weight rod/piston assemblies hanging on them.

 

Thanks for clearing that up, I could have sworn that I read that the 86 up sbc were externally balanced.