Kiln- As a rule if it's on a carb and streetable the 2 bolts are are O.K. You can also add a Blue Thunder steel main girdle (cleap) to help beef things up and a stud kit will help to. The block that has thick mains has the same casting numbers that was used on 429 - 4 bolt blocks and guys scower the junkyards to find them. They were used in trucks I think. There is several aftermarket 4 bolt conversions on both styles of 2 bolt blocks but be forwarned they all require machining on the block as far as I know. If you use a main girdle a custom
oil pan has to be also used.
cobrashock