Looks like a good fit up there.
Yeah, I've never quite trusted self-tappers either, but then again, have never personally had a failure and have always been surprised at their tenaciousness in holding things together.
Luckily in this any real impact forces are upward, but that is a lot of weight hanging off of them. My buddy used weld-nuts and 3/8" bolts on his installation and it seemed very robust. He just modified the existing strap, which is also a pretty strong piece.
If you didn't already, you might consider putting some "feet" on the tank's stand-offs on top. Sort of a slight insulating layer between the tank and the body. Lots of us have done this, using everything from conveyor belt material, to folded over bits of inner-tube, to polyurethane bushing strips, to in my case lengths of that fiber reinforced muffler hanger stuff.
It's not required, and the manufacturer intended the feet to be metal-to-metal with the body without trouble, but insulating it has not been a bad thing either. Especially if the tank's "shelf" in the front is coming very close to touching the frame's crossmember.
In my case, I had to do something because the stand-offs were welded on 90° off, so instead of straddling the body panel ribs, they sat down inside them and shorted out the sending unit!
But I liked the idea of some cushion anyway.
Getting past all the bolt-on vs J-hook thing though, there is absolutely nothing wrong with using the tank as intended, with the J-hook strap setup if that's what they send you. It's very strong and reliable as long as it's gutentight the first time. After that, the only down side is if you're beating on it hard like I said.
If you plan to land on it and use the gas tank to pivot the Bronco off of rocks, then sticking with the bolt-on theme is a good way to go.
Paul
