Rear Tires Suddenly Lock Up Going 65

I don't think the e brake had a problem, it seemed okay while I was under the car taking the tranny out. The clutches and steels looked really good. While browsing for kits online I noticed a lot of rebuild kits out there only include gaskets, clutches, steels, and the rear band, if any band at all. It's worth changing all friction materials when doing a rebuild.

I have access to a non-destructive inspection lab, would it be worth to have the transmission case and other parts inspected for cracks? I was thinking the case, the input/output shaft, maybe the planetaries. It was a quite a violent lockup. Happened pretty quick, didn't think about neutral. Both hands on the wheel and foot on the brake.

Phil