Help me win this argument 400 in a 72.

400 a boat anchor unless stroked??? Bigger bore than a 440, stroke of a 383. Sounds to me like if built right the dang thing would be a screamer like a 340.

But the 400 would need more to make it work. It's your call. If both the 360 and 400 need rebuilt then it all depends on how much extra work you want to do.