Super beetle vert / Seatbelts

[Cross]

I have recently purchased a 74 beetle vert. The interior needs to be restored, which is going to be my winter project. I need to put in some seat belts for the rest of the summer and fall. I was given by the previous owner boxes parts including seat belts, but for the life of me, I cannot figure them out. The back seat belts are there (sholder strap) but the locking mechanism's do not latch. The male part (strap) will not fit in the female end which bolts in the middle of the back seat. I have purchased, Chiltons and several other books, none showing seat belts. After market belts are fine with me, but I still need to know where they should install. Any help would be greatly appreciated. Thanks Cross