Bypass + heat absorbing tape on the exhaust + new insulation on footwells --- and potentially consider ACHi there
Just as a side note.
Have you considered putting in a heater bypass valve when you are in there ?
Just asking, as I recently got my car back on the road and have now realised that the car gets very hot inside even with the heater turned to off and that’s with a completely rebuilt heater system with all new seals etc etc.
I think I will try and retrofit a bypass to mine at some stage.