I think that the J20 box is the stronger box. It also has a quicker ratio I think.

You might have issues with the input shaft size/spline count and also with the hose connections on the box. Nothing that a few dollars can not overcome.

A quick search finds this page and some information from people who are more knowledgeable than me.

-- mike

CJOffroad.com - Steering upgrade? Wagoneer box?