opinions welcome on build.

What PRH says
WE did a semi crate engine program with 3.75 crank 6" rods
with a few 4" cranks and 6 " rods 4 " bore for 400 inches
They even ran blown fuel with that combination
and a very few with 4.250 cranks and 6" rods 452 with a 4 1/8 bore
The only ones we kept the revs down were the 452s ( and the heads did that )
But also what YR says about the chevy rod and inexpensive piston makes sense
some combinations just make more sense than others
lots of pistons available for 4" stroke and stock 4 1/8 rod
(but I'd go longer rod if it makes sense)