If you have the 063 396 oval port heads you are all set. Don;t worry about wether they have large valves. The stock size 2.07x1.72 valve are fine for aand even prefered for a 550hp street/strip oval port 396.
The 396 cylinder bore is small and gets shrouded with larger valves in closed chamber heads.
the 2.07 valves are the right valve size for your 396 with closed chamber heads. The key is correct head porting.
But the heads need to be correctly ported for power.
The 550hp Joe Sherman built street 396 is build using the 063 heads with stock valve size. (althou they are probabily hi quality Ferrara or Manley SS)
The larger valves work better when on a large bore 427-454+cid motor.
For your purpose, The 2.07 x 1.72 valves are the ones to use on a 396 with the closed chamber type oval port heads.
They flow plenty plenty once correctly ported. Check out the details of that build. It's very simple yet delivers the power using fully ported
063 heads and stock 2.07x 1.72 valve size.
If you are serious and you want to do it right the first time:
You may want to pay someone like Meaux Racing Heads in Louisiana. www.maxracesoftware.com
to correctly port your "063" oval port heads....
The cylinder head preparation is key and he can do it right for you.
The rest of the build is pretty basic,