Performers or AFR 165 should get you where you want to be Frank. Anything bigger and I think you'll give up low end torque for high RPM hp (Plus it might push the limits of the block). Since your not wanting to push it much beyond where you are now,.. I think a 165/170cc head should be perfect.

You were running really good with those E7's (They flow what,.. 140 CFM stock?). I really didnt expect you to see the MPH your seeing. I figured low 11's max. I had AFR 185's on my 306 with the Vic Jr intake. The cam was a Comp NX274HR rated to 6200 RPM. But with the huge intake ports (I had to trim Fel Pro 1265 gaskets to fit the ports) there was not enough velocity until after 4500 RPM to make the HP I was looking for but was still pulling strong even at 6500 when I let off. Ran a best of 12.33@111 NA with roughly 3600lb race weight.

With your Turbo I think something like Vic Jr or AFR 185 heads will put you beyond the limits of the block. John and Wendy made something like 570hp with theirs on E7 heads before they blew a head gasket,.. but with a bit more boost than what your pushing. I think blowing the head gasket saved that block .