the early '72/''73 "cold weather" blocks were supposedly the best of the 400's. Part number ends in 230 I believe. Had some thicker side ribs. Whether it's really stronger, who knows.
The early 230 blocks look really nice and have big beefy mains but the cylinder wall are not any thicker than other casting numbers. I spent a bunch of time finding an early 230 block years ago because I had heard that it was "the one". When we sonic checked that 230 block we found out it was junk. All of my money and my dreams of a killer block disappeared in a poof.
