If he likes it, I'd just replace the camshaft, maybe build a 2nd 8 3/4 chuck for it with a lower gear, and call it a day. With a cam that's a prety fun package.
Everything else was left stock including factory exhaust to the tips. Car ran 12.90's with a sticky on the back. I am sure there are plenty of other recipes but I saw this one for myself and it flat worked....
It boils down to what the owners expectations are. Personally the original drivetrain would go in the corner and I would go over 400ci but then you will be changing other aspects of the car and once that train starts moving everything changes lol.... Post some pictures of it if the car is all original. Hard to find a demon like that these days lol...