I wouldn't run anything bigger than a 350 jurnal on any small blk. In fact i run bear spacers on the 400 blocks and have for over 25 yrs. REASON, bearing heat, in fact NASCAR runs even smaller mains, i think Hink said they were running 2" mains VS 2.450 mains that a 350 has.
Hey Warren, didn't you know you could have bought a 2 piece adaptor for the crank you sold for less than $25.00.?
JMO
Zip.