69 front seat belt question

[johne3191]

Have a 69 with a bench seat and only lap belts ( way too tight to be able to use). One of my old 69's had a shoulder belt in the front and I would like to add this to my current ( and last ) 69. Will order reproduction but not sure how a 3 point system was supposed to go into a 69 ( trying to keep it looking original )

Any one able to explain where the attachment points are and what style is used in the 69?

Thanks

John E.