I bought lap belts from one of the repop sellers. Classic Parts of America, I think. Then I went on Ebay and bought three sets of the old spring wound chrome windup devices that slip over the belt and retract the fabric of the belt. The ones I bought had the "flip-up to release" tab and not a pushbutton. I installed three belts across my seat and there is plenty of slack with the exception of the middle belt. What I did is buy grade 8 flat washers, 3" diameter I think and fairly thick. I drilled through the floor under the seat right at the back inner part of the seat frame. One on each of the outsides of the seat frame for the female flip-up ends and then two more closer inside the rear of the frame for the driver and right side passenger male ends. I then installed the middle passenger belt under those inner bolts for the male ends of the other two belts. Each was bolted through the inside floor with a grade 8 bolt sized to fit the hole in the belt end, through the belt end hole, then a lock washer, then one large flat washer. Then on the underside of the floor, another large flatwasher, lockwasher and the nut. With the exception of a snug fit for one of my friends with a larger belly who sits in the middle seat, the driver and outer passenger have plenty of room in the repop belts. Very snug and seem to have plenty of strength to hold you back in the case of a panic stop.
