I’m guessing a 400 piston and rings with a taller compression height? I had a 1972 400 hp short block once that the pistons were just barely below deck, about.015 or so, so I’m thinking it was probably the same piston. I apologize for the de-rail, but folks I’ve talked to who have owned 400 HP that did the old school performance mods (TM6, headers, Crane Blazer 288/.480 cam, distributor recurve) claim it was more like a 340 than a big block. A whole of fun in a ‘72 charger with an automatic and 3.91 gears.