Standard dimensions for the BBC 396 was bore 4.094" (a 0.030" over would yield 4.124") with a 3.766" stoke.

 

Thank you.

 

You make a 402 when you bore it .030 over.

 

Tony, get all the specs and play with the Dynamic Compression Calculator. You need 8.5 to 7.5 to run pump gas reliably. I would do it but I don't know BB rod length, head gasket thickness, deck height etc.