If you are going to use the 12 bolt with the 3.73 then why would the gears and the differential in the 10 bolt make any difference?
I agree with the post above. The Power Trax Lock Right will work great in the mud and snow. I've had one in my truck for about 15 years and I put over 140,000 miles on it and it still works great. A clutch type differential like the Eaton can slip when you are off road and leave you stuck in the mud. The Lock Right will not slip, even if you have one wheel off the ground. I love the Eaton Posi for street use in muscle cars, but a locker works better off road. The Lock Right pops and jerks a little sometimes, but it's not bad. If you have an automatic transmission then you will probably not even notice it. I have a 5 speed, so I notice mine a little more.