Port the poop out of them. Change out the helicoils in the heads, install Timeserts or equivilent. Run about 225-250 seat and about 600-625 open.
I would use an 11/32" valve, as light as your wallet will allow, not saying you need to go titanium, but maybe a hollow stem Ferrea. Springs will depend on the install height with your valves, but I would use a PAC, PSI, Manley, etc. spring.