Yes you can sleeve all 8. The chevrolame guys are sleeving 454's down to 396. been going on for a decade or more.
I know of some 340 racers who were doing the same before new blocks were available.
As far as GM guys crying foul... let's go down the Mopar path... '62 413's with '64 heads and intake, '62-64 Max Wedge cars in any possible B-body combination you can think of, "Nascar" Hemis, trim-less hardtop Plymouths, Dodge hardtops with Sedan trim, AAR hoods on any fresh air package 1970 'Cuda, and my personal favorite...'66 Hemi cars with scoops. We probably wouldn't bring so much attention to ourselves if we didn't do such bogus things...
