How hard to change a 4wd A500 to "2wd"

There is a local truck for sale near me, 91 Dakota, 318, auto(500?) 4wd...395 000 kms. not a typo. :) There has been a lot of debate on the overdrive trannys fitting in an abody. Since this is 4wd, can I get something to make it like a 2wd or is a 4wd totally different. thanks