Can anyone tell me what a stock 1969 firebird 350 2bbl came with from the factory....was it a 2 bolt main set up or a 4 bolt main set up?

2 bolt.

So I guess the 350 HO and trhe 400's came with 4 bolt mains

nope. 2 bolt mains. Only RAIV had 4 bolt main caps installed. The bottom end of a Pontiac is very strong, only all-out race applications should consider 4 bolt upgrade. It's not necessary.

Agreed. Some 400 blocks came drilled for 4 bolt mains but actually were built with the two bolt main caps. The testing results came back that the 4 bolt caps were not needed after some of the assembly lines had already set up and drilled the blocks for four bolts.

I have two of those 4 bolt drilled 400 blocks. Neither was originally a Firebird block.

Some 428s also had 4 bolt mains. My original post was addressing only factory installed engines.