Seat belt interchange

A basic set of aftermarket belts will work much better. The cost savings wouldn't be worth the effort (IMO) of cutting up your rear panel and welding in an anchor to make the 75 belts work.

I was given a set of belts from a 75 Scamp for my 73 Swinger. After seeing how the 75 belts were made, I opted for a set of aftermarket belts instead.