How about this 360 LA combo?

I second the 1.5 rocker ratio. The combo you describe with a XE274 cam and a good flowing dual plane (I would buy the made in USA Edelbrock over the Chineese knock-off, but thats just me). You should have well over 400 streetable horsepower. Other thoughts... Subframe connectors; you will twist that little Valiant into a knot with that engine. A 904 will live behind that engine IF put together well, but a stock junkyard trans will go away pretty quick. A big cooler will help, especially if you run an agressive converter. Which brings up the converter, spend money here! 2500 RPM seems a bit low, there are some streetable, efficient 3000+ RPM converters being run by regular posters on this board, but they aint cheap.

Your son should have enough car to put the Mustangs away, and even get kicked off the dragstrip for not running a cage. Low 12's shouldnt be out of reach.

Keep the car looking totally stock on the outside, including steel wheels and dog dishes. BUT, take every "Valiant" emblem off and get a custom replacement made which says "Violent".