there is another style prop valve that has the rear adjust and front T integrated into one unit

http://www.summitracing.com/parts/wil-260-11179/overview/

but...FWIW, if it were my car, i would run a 73-6 disc prop valve (you can get them new on ebay for $79), and order pre-bent lines for a 73 duster and get the thing back together.