Someone needs to start re-casting 340 blocks

IIRC small block Ford Cleveland had smaller mains and was seen as the performance alternative to the Windsor larger mains. something about friction????
???? The Cleveland engine was the performance alternative to the Windsor period. If You mean swapping a crank w/Cleveland size bearings, & spacer/shim shells, yes, there is less friction. The 360 was designed ground-up as a cast crank unit, & in typical over-engineering fashion, Mopar probably made the mains larger to maintain crankpin/main overlap.