In the early 80's Reher/Morrison won NHRA and IHRA world championships 3 years in a row being the first to ever do it in the same year. They were using marine blocks. 500" for the NHRA setups and over 600" for the IHRA setups.
These days 496 marine blocks are more plentiful than almost any other big block and is a good choice for a build seeing they are intended for extended wot performance.
Hope this helps.