I used to use the Mopar brand ductile iron main caps on my engine builds that would make over 700 HP, they wouldn't stop the stock 440 blocks from cracking in the main webs between the bottoms of the cylinders into the mains
When Mopar quit selling them I looked into what replacement main caps were available and ended up choosing the 440 Source aluminum main caps with their ARP main studs and I have not had a failure in 15 yrs.
Milidon sells steel caps, but I don't use them due to the expansion rate differences between cast iron and steel: work:
The 400 blocks don't crack in the main webbings, and they have a bigger bore to start with than any other Mopar B or RB blocks also
Your best bet on making a safe drag race engine using a Mopar wedge type block is a new one in aluminum or cast grey iron: up: scope: Buy a KB, World, Bill Mitchel or whoever else you can get a new block from