With some research and talking to a handful of people that have done factory LA/Magnum engines with W9s. W9s actually had a 59° variant but they are uncommon and it's actually recommended to use the 48° on the 59° block. You have to do some ever so slight clearancing for the pushrod guides. Then have to use W9 Raised Port rockers for the proper rocker offset. Not too hard based off of others experiences. Spacers must be made to make the intake fit but that's not a big deal.
Also I'd love to read your articles you mentioned about SBM taking 1,000 HP. I love to read info like that. Actually was just discussing with my coworker about using the Borg Warner S475 he has sitting on his shelf and upgrading a Magnum 360 to 375 HP before turboing. Using the math formula for turbo hp ((20 psi ÷ 14.7) + 1) × 375 N/A hp = 885 Turbo HP.