47-55.1 under bed tank

[Marty68]

I am wanting to ditch the half barrels as fuel tanks. what tank is preferred.
does someone have a picture of the tanks inc unit installed? how much room is there between tang and differential if installed with spare tire crossmember remaining in truck?
where does the filler neck come out, how far forward, in the bed?
my rear is triangulated coil with shocks mounted to the rear of dif. taking up a few inches. I would not want to mount take where it had to be removed to service rear end..

I understand the mustang tank fits well and is a bit bigger but I don't think I can leave spare tire crossmember with it.