So when I said I had a 30x 9.50 that is not a 30 " tire In the stock location .... Your confusing me a little bit

Taller, no. Wider, yes. 30.05 x 10.04

It's actually about 29.5" in diameter.

Thank you for clearing that up

Different tire models wind up with different ODs. 30" is a nominal measurement.

Is there anything special about that factory mount? In a crash I'm not sure I want 40 or 50 lbs of tire tapping me in the back of my head.

Between the mount itself and the seat backs, you're being overly concerned.

Not the mount per se, substituting the all-thread. I plan on leaving this world intact, not in a "persistant vegatative state".

The mount itself is a bracket welded (maybe bolted, can't recall) onto the frame under the trim back there. The arm that goes through it is a steel rod with a flange on one end, bent into a sort of L shape, threaded to take a retaining nut and the big plastic ****. It's pretty simple and can be bolstered up for the paranoid. But really it just has to keep a 60 pound mass still (30x9.5R15 on a steel rim), the tire is too large to fly over the rear seat. Honestly I have less confidence in the rear seat latch lol

Actually, it's just rounded up from 29.5".

Bracket is bolted down, four 10mm bolts I believe. Or might be 8mm. Can't remember exactly.