I ran a comp xe264 -hr14 (.512 lift) with gt40 heads (1.94 /1.54 valves) on a stock bottom end 86 and fel pro 1011-2 head gaskets (.038 compressed thickness), just make sure you check piston to valve clearance
also ran it for a while with 1.7 roller rockers on stock HO cam and the comp cam, both cleared ok
whether you will gain any performance switching cams with the E6 heads is doubtful
, there is a list of speed density compatible cams available if you google
Custom cam would be best option as the grinder can tailor the timing events to clear the pistons.