I dont know, Chrysler did wierder stuff with their cars before. Ive seen a 73 duster with a factory 225 slant six and a factory 8.75 rear end....according to everyone else it wasnt supposed to have a 8.75 at all (since the last year for 8.75 was 72), but it did and it was origional, the owner knew it had never been swapped out since he bought the car new off the lot. Its possible that car you had came like that from the factory but Ive never heard of them doing that. It woulda been nice to just do that with all the cars. I dont see any benefit of chrysler using sbp on any of their cars. It wasnt cheaper to produce, then you had to make 4 inch bolt pattern wheels for the cars, not any any benefits too it that I can see