I will avoid going down the path of changing pistons because these are new and if i do another rebuild it will be taken out to 463 ci. l guess the cam change is the answer ( shame really, this XE268H pulls hard even with stock 7j2 heads, and sounds great)..
We do have e85 around here (somewhere) but again, the Holley is new.

Im not sure of engine specs as this was rebuilt 2+ years ago by the person i bought it from. He did say it was built to factory specs with stock parts on a std bore. I threw the cam/lifters in as they were excess from a 79 T/A build.

Do you think chamber work alone will see me right? ...nothing major, only minor blending and cc'ing each chamber for consistancy, because that is easily do-able as the heads are on the bench