ohno50

I'm new to the forum but have had my 89 Fox Hatch for a while. My problem is that the 89 only has lap belts in the back seat and I don't feel comfortable putting child seats or booster seats in there without the 3 point seat belt, or even when they get older for that matter. Had I known this a long time ago I would have bought a 90 or higher stang but here I am and selling it is not an option.
I am wondering what I can do to make it safer for them. I bought a used set of 93 rear belts with the 3-point system and I'm thinking that maybe I can have a bar welded in behind the back seat(maybeacross the shock towers)so that I have a structurally sound mounting location for the shoulder strap part.

Any help and/or pictures would be greatly appreciated!