The mex blocks are a bit stronger, but not that much stronger. And ~500hp is considered max for most 302 blocks with a conservative tune. Honestly, once you're trying to get that kind of power anyway, you should be building off of something like a Dart SHP or FRPP block of some sort.
Who cares how much horsepower it has, all that matters is how fast it goes!
Untested 331, lots of suspension, chewing up corners.