Pictured above is a copy of the original Ford drawing for the 1929-31 Ford Twolite headlamp reflector (single bulb).
The optical performance of the reflector cannot be optimized with the wrong parabolic shape or dimensions, nor with the use of higher powered halogen bulbs. It will just result in low performance high glare headlamps. They may be bright with high power bulbs, but they cannot focus and put the light to the lens in the proper direction. The result is just light scatter and glare.
The bulb socket is adjustable fore-aft in the reflector via the screw on the back of the headlamp housing. This allows the bulb filament to be properly placed at the correct focal point of the reflector for optimum lighting performance.