Mounting Rear Gas Tank

[stich]

I've got a '49 Willys and purchased complete tank and skid plate assy for a '76 CJ5 thinking that this was the tank to use. That tank is 10"x 16"x 22" not including the skid plate. Well the frame of my Willys is only 15" clearance from front cross member to the inside of the rear bumper. You can see the dilemma. I already cut out the the draw bar crossover to see if the tank will fit up inside to no avail. The rear of the skid plate mounting holes stick out past the bumper. The only solution I see is to cut off the rear bumper and add an after market bumper onto that. That way I can bolt the rear of the skid plate under the new bumper. I also looked into moving the front cross member forward but the tank would hit the rear end if I moved it anymore forward. Who else has done this to their Willys or early CJ's? Are the early CJ's different dimensions between cross member end rear bumper? Any suggestions?
Thanks
Jack