Your first car upgrades? (Electrical/Mechanical)

I have a friend who is a machinist and works on a limited number of old Mopars as a side gig. Before he will do any upgrades to the drive train, he insists that the first order of business is to upgrade the brakes. Depending on the projected future of the car that might mean factory style front discs, or an aftermarket kit and the best rear drum rebuild that is available.