By just looking at the parts book, and not having the actual parts before me, it looks as if those pants originally designed for pre 1975 tubed gear will fit all previous models. And that the pre 1971 brackets can be easily modified to fit the newer model tube gear. Brackets and pants look to be interchangable until the 1975 model year. (A minor cut out of the pre 1971 brackets would be all that is required.) In 1975, they completely changed the brackets so they will only fit the 1975 and later pants. Mr. Ed is the very first 1975 model. So, thus the first 150 with the changed brackets and pants.
So, if anybody out there have any pre 1975 wheel pants brackets that they would like to sell me??