I took the throttle passthrough apart from the firewall side and used the die grinder to smooth the screw holes and the eyeball hole. The passthrough was reassembled and I was able to get all four screws lined up this time. Before tightening them, I installed Adel clamps on the carb heat cable and the throttle cable and fastened them onto the bracket riveted on the instrument subpanel.
The throttle firewall passthrough tightened up
The carb heat (left), throttle (center), and mixture (right) cables fastened to subpanel bracket
