A large amount of Pontiac blocks are drilled for 4 bolt mains but only have 2 bolt caps. It wouldn't be something to worry about adding them unless you intend to make a high rpm engine out of this 455 (6000rpm and up). I'd worry about the stock rods looong before I'd worry about 2 bolt mains, very smart move to trash the factory (CAST
) rods and go aftermarket forged.
Crower (not Crowler) is a really good company, I have used them for years, one of the early forefather companies in the industry, been around a long time.