Carnage in rear after M/T ET Streets Hooked

Well, I installed my inboard spring relocation kit, measured, remeasured, set pinion angle, and on went the M/T ET 275/60's. MiG welded the spring perches on.......BIG Mistake!!! Took it out for a test spin, and after a 2nd launch and the Mickey's bit, snap crackle pop....Violently! Broke the welds, snapped the U-joint, shoved the pinion snubber into the floor pan and broke the snubber, and damaged the driveshaft. All that work, it broke, now I'm bummed and discouraged. The 408 combo is nothing to take lightly regarding driveline integrity. I posted this so no one will make the same stupid mistake I did.