For me I'd never build a 4" stroke small block, To me bore stroke ratios and rod ratios still matter. Plus theres not to many good heads for 400 plus small blocks, thats why after peak hp numbers the curve takes a nose dive. I'd rather build a 383 or 400 than a 408-416.
So for me I'd go no bigger than a 3.79" stroke small block. If I wanted bigger than that I'd go stright to a 500-511 built from a 440.
But thats just me, I see why people build 408-416 and thats why I said he's probably better off building that.