which one would you choose the stock cooling system or a aluminum radiator

Hey group currently i'm running a aluminum radiator 22" with a hp 180 thermostat and I've also installed air conditioning this year. The problem I'm having is when I run the air conditioner the thing will heat up to 195 and stay there for awhile and than slowly go back down to 180 and it will do this while driving down the highway. I'm also running a shroud with that radiator. When I run the car down the highway without the air running it will run right at 170 to 180 and stay there. My question is should I go back to the stock radiator three row with a shroud and install a oem stat and see if it will stay at a constant temp instead of fluctating up and down on the temps. The motor is freshly down it is a 408 strocker so I know that it is all flushed out. I'm wondering if it is the HP thermostat that is opening and closing when it does that fluctating of the temps. What is your guys thoughts.

Pat Faley
67 Barracuda NB
Peoria IL