Grant, you better drive with a door propped open, you can bail out if she blows."Scotty here Captain, she can't take much morrre of this abuse"
I have no experience with an 80 over 261, but Joy has a stock 60 over 261 in the 51 truck.The truck pulls a 1500 lb high frontal area travel trailer on summer trips.The truck never runs over 210 degrees even when pulling the trailer up hills steep enough to require down shifting .And the radiator is a standard cheapo reproduction not a heavy duty "desert cooler"
Grant again,although piston weight doesn't affect the balance of an inline 6, I do know inline engines running larger oversized pistons tend to run a little rougher than smaller bores.Perhaps you might want to compare the weight of .080 pistons to standard pistons.Hurry up and get that engine finished so I can blow by ya in the 37 lol.