I have been looing to change to 3.91 gears. I have a 3.23 suregrip 742 in right now. I have been watching ebay for a nice 3.91 stump but they always go for quite abit of money. The last one I bet on went for 530$ plus 50$ shipping. I was going to rebuild mine but I thought I could get a complete one for cheaper. Then I would have two. New Gears are 200$+120$ for new bearings+new clutches 60$+getting someone to install it 100(ish?) that is a little cheaper. But, If I rebuilt mine It would be basically new. If I bought another I would have two and I could swap to 3.23s for long hauls and things. I also have a spare 489 case that would need a suregrip and gears also. I think this is the next mod I need but now I'm not really sure. It's pretty hard stomaching all the money for 3.91s when I bought my 3.23 stump for 150$. After I swap gears I am wanting to purchase a PTC convertor, racer brown cam, and a set of Mickey T street radials. I am wanting to drag 1/4 mile but my car is mostly street driven.