340 or 408?

Turk, I think you and I are on opposite sides of the coin.
Engine masters did a comparison test of a 500hp sbc, and a 500hp bbc.
The 363" chevy rpm-ed like mad, cost about half again as much as the 454, needed better gas and much more gear.
The 454 made the same power, WAY more torque at street car levels, and would have been much more livable on the street, cheaper gas, better mileage, less freeway rpm. (and I believe if optimized, faster at the track)
I suspect you would take the 363, with 4.56. I'd take the 454, with 3.55.