What you add with small closed chamber and a increase in compression, the smaller valves and port flow will make it all go backwards. Keep the #302's for the 273/318's.
I would use a set of old 67 273/318 920 heads... They are closed chamber... And not prone to cracks...
I had my head guy do up a set for one of my 318's that I'm building and he ported them and installed 360 valves in them that I had left over from converting 360 heads to 2.02" intakes... Install the 1.88" intake valves, 1.60" exhaust valves (with hardened seats) in the 920 heads and give them a good port job and they will flow as much as a stock 360 1.88" head or better...