[OrrieG]

Yep. you can have a spare tire OR gas tank there. Most aftermarket ones are 19 gallons, which keeps the bottom up out of harms way. Some guys use larger capacity 70's Blazer tanks. Fill options are up thru the bed, back over the bumper, or thru the side. Using the box above click 67... and search for "1950 under bed gas tank", lots of threads will come up for you to review.

If you want to keep the spare there and get the tank out of the cab you can add one in the bed, guys use old footlocker, coolers, tool boxes, etc. to hide them. Or you can look for an early Suburban that mounted in front of the passenger rear tire and fill above the step. I think the big trucks from then also had the side tank but can't remember if anyone has used one.