Hey there guys,
Dont try to depend on just a "by guess and by golly" method of popping holes in the floor. If by chance your ever in an accident (God Forbid) you want them to work and not ripp out of the floor. Then you go through the windshield.

This site has full kits very reasonable for retro-fitting older cars with seat belts that will work correctly for your setup.
Im sure there are others that are resto quality ($$$$) but this IMO is the best all around price/quality sets on the net.
Seat Belts
Here are some install instructions. Your specific instructions may not be this particular link, but this gives you and example.
Retrofit Seat Belts Installation Shoulder Bolt Anchor Point Your Classic Car, Hotrod 3 Point Seatbelts
Just remember that your trying to save your life by installing saftey belts, dont do it half-assed. Ok??
