Ken....I built a '91 Jag XJS rear. I centered the pinion between the wheel flanges by offsetting the right side pivots 2" and then shortened it 6 3/4" on each side to achieve a 50" width. The rear torsion arms will ride on the Jag lower arms. I built this adaptor to connect the 350 Turbo to the Jag chunk. That keeps the setback at the standard 40" (back of SBC to centerline rear axle) and the wheelbase at the original 86".