I get why people do a 408 but never made too much sense to me, since we got 383/400/413/426 all great 400 ish cid engines even a 361 (4.125") with a 3.75 stroke gets there. And you don't have to worry about underheading the engine.
because a 408 hooks up to your current transmission can use your current mounts and exhaust, etx etx etx
yeah, cubes will [almost] always win out but when you have to go back to square one and lay out a bunch of cashish all of a sudden staying in the same engine family makes a lot of sense.
and you can just press the easy button, melt a credit card and have a 408 dropped on your doorstep.