71 Duster 360 turbo build

Well it didn’t blow up, but the dyno session didn't go great. The transmission was slipping pretty badly. It doesn’t appear to slip on the street, but I’m guessing it will soon.I got only one partial graph.18psi. 584hp at 4112 rpm.We tried 2nd gear and it held for one pull then slipped as well so I’m guessing the rear clutches?