400 block
Don't be to scared of that 2 bolt 400 block. I ran them in bracket cars and nitrous street cars for years with no problems the last one I had was a studed 2 bolt block with splayed caps ,filled to the freeze plugs . That motor was .040 over with a reworked stock 400 crank, aluminum rods ,14-1 ross pistons .227 afr heads, and a 2 5/16 hilborn stack injector on alcohol .
I ran 8.0 @160 with that motor in my 235" dragster and that motor went to 8600rpm on the burnout every pass with no problems to the block or crank.