Why not a 413 ?

^^^Right On!^^^ Or, use aftermarket crank rods with 2.2 inch crank pins & .990 pins and take your pick of 4.25 inch chebby pistons. Find used parts and over the counter cast pistons while paying attention to your bob weights and you may be able to come up with a stroker on the cheap. i.e. 4.25 bore 4.25 stroke=471, doing it with the available 7.1 inch rods gives it a rod ratio 1.71. This combination should make great use of a fast rate of lift solid cam when using stock port window heads.