I never did one for tech inspection but I've welded up some broken seat backs on stock buckets. On my 72 a-body the plastic back unscrews to reveal the stamped frame with the covers hog ringed on. I don't see why you couldn't reinforce the seat frame and T off of that to a bracket that would poke thru out the back? It wouldn't have to add that much weight and the factory back would just have one new hole in it.
