The CJ5 and TJ frames are very very different as well as the suspension in each of them. The TJ frame would be a lot stronger.
Thinking more into it, if a manufacturer offered a V8 from the showroom it would have the necessary safety and build features to support the power and torque. They wouldnt offer it blindly as an option. I belive DOT has a crash test and other safety test for each vehicle and the different options in them.
Yeah, I guess that is my point. The Wrangler frame may not be built for a Hemi, and the mkting people probably figured out that the cost to make it "safe" would outweigh the potential profit.