1971-1973 Motion Vegas

[KXW]

Do you all know if Mr. Joel Rosen used 12 bolt rear-ends in his Vega cars? If so, any clue as to what the code would be? This past weekend, I attended a local swap-meet where a vendor was selling several high performance items, including a 12 bolt rear-end. The vendor stated the rear-end came out of a specialized 1971 LT350 Motion Vega. He said, he removed it from the car before the car was scheduled to be crushed/destroyed. I checked the unit for codes in the usual spot (In-side the passenger axle), but could not locate any numbers or code. The only letter that I could find at that particular location was a letter "B". That was it! Maybe the code is in a different spot? The axles appeared to be professionally or factory cut, etc. Personally, I'm not familiar with these Motion cars. Did GM ever produce a special rear-end specifically for a high performance Vegas? Or did Mr. Rosen add any special markings to his rear-end components? To your knowledge, is there any way for me to verify this 12 bolt rear-end as a Motion unit? Any help in this matter would be greatly appreciated. Thanks for the information in advance!

P.S. In your opinion, what would be a fair price for such a Motion item? The owner is asking $400 for it.