hi,did you know that you can fit akmost any a10 barrels to your engine,which would normally have the type with rounded finning.i personally would look for some later,larger finned[squarer looking]barrels,thin flange type will be fine if you keep the compression at about 7.25 : 1.of course with these barrels you will need a matching shape later head,i find these are easy and cheap to come by,i have about 3 of these iron types.