Sonic test results
First off, did the machine shop provide their recommendation? Those closest to the work, with the most experience, typically have the best ideas.
Center/Back of “cylinder 1” is your thinnest on both, with a twenty thou advantage on the 77. With that in mind you could go 40 over on the 77 and be where you’re at in the 79 without having touched it at all. My
opinion for a mostly drag build be to go 60 or 70 over in the 77, leaving about 150 at the thinnest part. This is still less original material than you’d remove putting in a 3/32 sleeve.
Also keep in mind that “center” is roughly 3” down, which is pretty much bottom of stroke. Most of the high energy from the ignition event is gone and bleeding out from the exhaust valve opening, and the intake valve is still hung open at the bottom of the compression stroke. More
opinion here - ring seal and bore distortion down there have less impact on power output.
Last but not least, the water comes in right there so cooling should be sufficient to mitigate a hot spot.
