77 Longbed TBI swap. Have to dump the outside frame saddle tanks. Anyone else done the TBI swap on a longbed, what TBI tank did you use? Anyone mount below the frame rails? Frame rails under the longbed are 27" wide. The only TBI tank I have found to fit in between is a G20 Van tank which measures 22 x 31 x 12 3/8 and holds 22 gallons. I'd rather have a larger tank but it would have to sit below the frame and that seems like a bad idea to me.