There are a few reasons to dislike OEM 67 belts as shown above. Huge belly burning chromed buckles. Spring loaded hair roller like thingy mounted on the front belts serve as retractors. 68 and later have vinyl cover glued onto the same metal buckles so only a little better. Spring loaded retractor housed inside the floor mounted plastic appeared in 68 also.
If I currently had nothing, aftermarket 3 point belts would be my choice. Might be a little more effort to install but at least you'll avoid the large metal parts banging on the doors, etc...
One important point I failed to mention... 67 buckets do not have latches on the seat backs. This means the seat back would go forward with you in event of collision.
Increases the force against a shoulder belt. I will not be held responsible for a portion or extent of injuries resulting from comments made here.