What are the differences between a marine bb and car bb

[glassman]

The time has come to rebuild/replace the engine in my 74 Keaton. Its currently a 455 Olds with 10.25 and a 442 camshaft, its a "Pack-a-jet" sold in the 70's which included a jet.

So, i'm probably going to convert it to a bbc or maybe an ls. Want the torque and ease of a bbc, parts are easier to find. But, i dont know the differences between a marine engine and a car engine. I know the externals are different for Coast Guard/fire & safety.

Any ideas on the long block part?