Temp gauges and only theory behind brakes is the previous drive I had to pull over due to the same issue but the brakes were smoking and since they’ve been bled again but still think they make be stuck slight on
That for sure indicates a different problem with your brakes.
You first need to check that the new brake booster does not apply force to the brakes when brake pedal is not depressed. I understood you put a 80s into your J7. Not sure about what the dimensions of the 80s are, but probably the dimension of the engaging piston are different or not well adjusted.
- Check the manual: Procedure to check on pedal travel and booster tobe behavior is described there.
- Jack it up, tranny in neutral, hub locks free (if fitted), and try to rotate each wheel manually: None should bind / almost no grinding noise.
- With brake pedal not engaged and engine running, there should be only very little discharge of brake fluid from the bleeder when opened like for bleeding brakes, as the system is supposed to be pressure-free when not braking.
- You probably can also check for the vakuum valve in the booster to shut properly, but I have no idea on how to test that.
(Can all be done only if your brake pads and disks have not been destroyed by the incident. If the brakes overheated, you nee to take it all apart and carefully inspect. Probably get an expert involved).
The new booster probably had pushed a piston to an corroded area it has never been before and now got stuck there. But its unlikely this happens to multiple wheels. I understood all brakes or all front brakes got hot? Then I'll recon the booster to be the culprit.
Dragging brakes do require the engine to work harder, but I doubt this would cause overheating. You would notice the smell of burned brakes well before.
I recommend to address one issue at a time. First get the brakes right and then do another shake down run and monitor the engin temp then.
Good luck Ralf