Static CR = 8.0:1 with flat tops, dynamic CR will be low, probably <120 PSI.
Summit 2801 will be too much cam for this combination.
Look for big-valve, 72 CC heads and mill them to 65 cc for use in Germany with 95 Octane bensin.
Heads such as: #670, #16 - 1968, not 1970, #62, #12, #13, #31, #997 would be far better on the 350, in my humble opinioin.
However ...
You can open the seats for large valves, you can do some porting work on the heads and you can have screw-in studs installed, but the amount of performance improvement will be limited because of the relatively deep chamber and the port designed into the head. For the amount of money it will cost you to convert these heads over to "performance" heads, you are far better off buying prepared heads of the correct type.
