Lildog, stock belts suck, at least in my 67. Canuck64SS has been doing some work on this and has a preliminary rig in the works. I find that my stocks belts don;t have the right length. The buckle ends up right at the edge of the seat.( where it feeds through).
Now, your 70 should have seat belt mounting holes just under the rear seat itself. You should be able to use these. Steve's going hog wild with a flat piece of bar stock. It'll be bulletproof and I intend to copycat him once he works it out. But like Leo said, you can get an aftermarket set and you should be able to bolt them in the existing mounts.
[This message has been edited by Gene Chas (edited 08-10-99).]