Gear Venders makes a planetary geared 0.78:1 overdrive which is pretty short, 12.5" I think, that might work pretty well with a bobbed 4x4 A3 if the wheelbase is 140-150". http://www.gearvendors.com If you're bobber's rear axle is in the same position as the intermediate tandem axle of a 6x6 I think you'll have prop shaft problems even with CV joints. The Gear Venders box is rated for 1200 hp and 30,000 GVW so should be okay with a deuce. Pricey though.I think you are mistaken. See the link below.