Miszny:
[1] Leave the heads alone. Run it like it is. If you look at other aftermarket parallel valve heads [ Chebby, BBM, Pontiac, Ferd Windsor, etc ], they all vary slightly in the combustion chamber design....but all run well.
[2] I have had 8.5:1 engines detonate on 98 fuel, but my 9.9:1 engine doesn't detonate on 91 fuel. You have to run it to see......
[3] I agree with installing the cam straight up on 108 ICL because of the cam duration & 3.9 gearing.
[4] Did the E heads come with beehive springs?