I think you are right, we have no chance of storing a full size spare in the stock location. Might as well keep an eye out for a 44 gallon Excursion tank to swap in place of the stock 16 gallon one, they do not hang any lower than the OEM spare did.
I would like a swing out for my truck to compliment the topper but first things first is the suspensionectomy.
Back to your question:
- My Dad ran our Suburban spare off the front bumper when I was a kid since the kitchen box was mounted in the back. He never had any overheating issues, even with a 454 in the deserts. I know this would be real tough with your bumper and planned winch, so I do not think this is going to work.
- Roof, I think not. Toyo lists the 315 as 71lbs +25 for the rim, no way you are lifting that easily on to the roof.
- Hood, LR style? (See above 'roof')
All I can come up with is inside! Do you really use the rear seat? You could ratchet strap it up against the rear window and build a removable L shaped platform around it, two pieced, about the height of the armrest on the 40/20/40, dogs on top of the platform with storage underneath.
Truck looks great, glad things are coming together on your build.
Cheers, Chris