Gas tanks strap mount points

I'm assuming your tire well is a rust bowl like mine was. Not sure what you have left from your description. Sounds like your bigger problem is fixing the bottom of the spare well. Heres what the bracket should look like. Made of three pieces. The folded down parts are sandwiched together to form the tabs for the strap bolts underneath. The keyhole in the top is for your spare hold-down. You might be able to find this in a yard. If 'original' appearance is not important you can make a very simple bracket as stated in first reply. Take good front/back measurements of what's left of the remaining hanger before removing. The distance apart can be figured from strap spacing.
Short answer - somebody needs to fab and weld...