When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
a 383 is a 4.030" bore with a 3.75 stroke, which means its a 400 crank with a 350 block bored out .030".
I think you can go .030" more on a regular block to make a 388, anything bigger requires a 400 block.
But i think GM makes a line of Rocket Blocks or other racing blocks that can be bored out bigger, but theyre way heavier, and i dont even remember if they are 350 blocks or 400 blocks or both.