The lap portion of the seat belt attaches to the seat frame. This point is above the fuel tank cover so there are no clearance issues. This is true for both lap and 3-point belts.
Go to your local auto salvage yard and pull a transmission cooler off of a smaller car. I used one from a Ford Taurus. Can be mounted on the driver side fender without drilling any additional holes if I recall correctly (but that was on a 77).
Just to pipe in on ride quality. I have a new set of OME springs from Kurt on mine. Great on the highway. Not so much on bumpy streets in town. I own it because it is a Land Cruiser.
If you want something that rides nice go buy a '76 Cadillac. Same vintage, same fuel economy, same looks...
Our local True Value hardware store had an assortment box in one of those bargain bins. The only ones not in the kit are the small radio size. Not an issue here as I don't have a radio...
Birfield - rock crawling when I should have had a DD. Fixed it and wheeled on.
Rear pinion - still not sure on that one. Fixed it and wheeled on.
Transfer case nose cone - keeper bolt on front diff pin not installed properly. Pin worked its way out until it finally contacted housing. Very...
If it were my project I'd suggest sandblasting the frame and determining what all needs repaired. You'll be surprised at what the rust is hiding. From there you can make a better call if it is salvageable or not.