318-3 Closed Chamber Truck Heads

Nice find.
Is the exhaust seat face at 45° angle? It looks less than that.
A 3-angle valve job would help flow in that area.

Flowing air/exhaust doesn't "like" to take corners that are sharper than 15°. It causes turbulation that will slow down flow.

I would also smooth the transition into the port and get rid of any sharp edges. Also in the chamber itself.