Need 1973 Duster Front Bumper Measurement

No. As mentioned, '73 and a lot of '74's had regular bumper brackets. Late '74 model run started using the "5mph" bumpers which stuck out more and used shock absorber style brackets in the front. All '74's on up had the shock absorber style brackets on the rear.

The later bumpers also have massive & heavy bracing inside. Bolt pattern of the carriage bolts on the surface is different so the bumpers don't interchange. I believe the later ones have an extra pair of carriage bolts near the top on either side of the front license plate area.