Cool. So shoot for 88.0-90.0% of the valve diameter. If they were mine I'd take them back, but I think my dad is finished making trips back to the machine shop. He's is in the "...they're Cobra Jet heads, so it's going to make tons of power by default" camp. It's probably a 400ish hp build if the exhaust isn't hindered by the seats.
It's a 401 with approximately 10.07:1 compression (averaged between chamber sizes). Ferrea valves, 3 angle valve job-- probably 11/32. Harland Sharp rockers, light porting (CO80-N heads), Rpm intake and cam, 800 Edelbrock carburetor, truck headers.
The machinist has supposedly built FE strokers that dynoed in 500 hp range with stock castings, so he either knows what he's doing, or isn't truthful.