I could be wrong, but I "think" your 63 should have the mounting points already welded into the tunnel and heater channels . . . and maybe even the door post. If the car never had seat belts, they will be covered by the carpet and vinyl. It might have been a year or two later before they started putting the seatbelt mounting points in 'em, but if I remember correctly, the 63 I used to have had them. David (a.k.a. the Godfather, a.k.a. RetBugtech) should be able to tell you for sure.