My builder made me a 442ci couple years ago out of a 400 block. The block was filled, strapped, and never had a problem with 780 hp. I found a talldeck rocket block for $500 and made a 472 sb2.2 headed smallblock alot stronger no fill in the block, splayed, and it was like night and day for the power difference.
the 442ci is a 4.188 with a 4" swing, grinding is a must on the pan rails
Anthony