I had a 14 bolt FF rear diff. sold to a guy for $175. I pulled the cover to verify the 3.73 gear ratio, and found out it did have a Gov-Loc. The fluid that came out was mud brown in color, and I know that it acted like an open diff. when I drove it. Would it be worth keeping and swapping ring and pinion (I need 4.10's). ? or should I just sell it as-is for the $175?