SPARE TIRE WELL OR NOT

Unlike 68 and later, The 67 has one tank strap left to right, attached to frame rails. Deleting that spare tire well should have no effect on the fuel tank. A different/larger tank could be doable if you can work out the filler neck fitment. The black plastic tank under a 96 Cherokee looked like it could work once the spare well is deleted. of course its 2 front to back straps would need to be used. There is a section of rubber hose between the filler door and tank so maybe a custom made hose?
Typical radial tire wont fit under the cover board but a space saver spare will. The hook on that 67 bumper jack is hardly a hook. I did use it once many years ago. I hope to never use it again.