most decent machine shops have zero problems drilling and tapping the crank snout for a retainer bolt , if you hand them the crank, which will make installing the ballancer far easier than beating the old one on and damaging the thrust bearing in the block,(BTW ID specify the larger BBC bolt size with the 7/16" NF threads as its stronger than the 1/2" NF the standard SBC uses)
but naturally that requires removing the crank, replacing the bearings,rings gaskets and probably resizing the rods, and if your going thru all that effort on a 302-327-350 Id suggest you get a internally ballanced 383 stroker rotating assembly with the main bearing journals cut if necessary to accept standard bearings for that block to replace it and gain a BUNCH of hp while your in the process
you could very easily gain 50-70 hp going the stroker route on a smaller displacement, thats a 40 year old crank and rods its seen some stress and upgrading the rotating assembly may be a good idea.
but naturally that requires removing the crank, replacing the bearings,rings gaskets and probably resizing the rods, and if your going thru all that effort on a 302-327-350 Id suggest you get a internally ballanced 383 stroker rotating assembly with the main bearing journals cut if necessary to accept standard bearings for that block to replace it and gain a BUNCH of hp while your in the process
you could very easily gain 50-70 hp going the stroker route on a smaller displacement, thats a 40 year old crank and rods its seen some stress and upgrading the rotating assembly may be a good idea.