[OKGMC4]

I love the diff vent idea. I'll have to steal the idea.. that you stole. I don't think that cross member will take a 4 inch shaft. Mine wouldn't fit if it were any bigger at 3.5". I mean, it clears, but I'm 99 percent sure another 1/2" might rub. And that's on a static 6" drop spring, not bags.

And on the fuel tank...I did almost exactly the same thing on my 56. I bought an aluminum tank and my father in law made rings to mount a vortec pump. Truck has run flawless for years BUT when the tank is full fuel seeps out of the cork gasket he told me would work. Never caused issues but you can sure smell when I fill up. Hopefully you are using a proper rubber or O ring seal of some kind so you don't suffer the issue I've dealt with.