OK, this is what my research, along with the help of knowledgable others here, has shown me:
1. Pre 1974 wheel pants are interchangable using the stock backing plates of that year of aircraft.
2. Tube gear backing plates will fit on the flat gear but not vice versa without minor modification.
3. 1974 wheel pants and newer require their own backing plate. This combination will fit all 150's.
So to fit the pre 1968 wheel pants that I have to our 1975 150, all I require is the brackets from a 1971-1973 aircraft.........
