Before you do the paint and powder coating, run all the brake lines, fuel lines, electrical wiring, etc. Install the engine, transmission and build the exhaust system. Actually best to "build" the entire car first, then take it apart and paint it. Don't forget the little things.....seat belt anchors, e-brake handle mount and cables, fuel tank mount, radiator mounts, drive shaft and safety hoops, master cylinder and pedals, throttle and cable, and on and on. Dang shame to have to be welding and drilling on a frame AFTER it's all painted.