Dana 60 gear swap

[lower50's]

The carrier split for a dana 60 is 4:11 and down so you will be fine with what you have. If you built your motor you should be able to do the gears, just takes time. I put 4:56 gears in my Jeep Dana 44, never done gears before, no prob for 10 years. If you want a posi I would go with Eaton detroit truetrac, very good posi no clutches to wear out. Here is a gear calculator I use all the time, just enter in info and use the Dana 20 T case 1:1 high range. Then go to bottom of page and that is high range speed and rpm. Hope that helps
http://www.grimmjeeper.com/gears.html