10.5 to 1 pistons

No, the 273 4bbl pistons had a thinner wrist pin IIRC that made the balance the same as the 273 2bbl that had massive pins. Even the 318 poly pistons were the same weight so they could keep casting the carry over poly/LA forged crank. Someone chime in if they know thats bogus as I only read it but can confirm the 273 2bbl pins are really heavy. The 10.5's should slip right in. You want to run premium for the rest of its life? EGGE makes 10.5 273 pistons but cant comment on them. Hydros dropped right into the old LA's, probably just a change made by PO.