Why do you say that? They are out there. Look on Craigs List, I found two for 100 bucks each and built one for my 74 Dart Sport. It's a B body rear and it fits perfectly with the perches moved in to match the spring width. I took my time, gathered parts and rebuilt the center section. I now have an 8 3/4 3.55 sure grip in my car for a shade over 600 bucks.
One of the pluses was it moved the rear tires out enough to match the width of the front track. If you currently have the 7 1/4 look at the track width front and rear, the rear is narrower.
