If it were mine I'd prefer the 4 bbl rod over the 6 pack but that's JMO.
If your shooting for .040" quench I'd suggest getting the rods center to center equalized (re-sized & new bolts of course).
Then measure how far the piston is in the hole.
Have the deck cut/squared for the steel shim head gasket and .040" quench.

I have no idea on what HP it'll make