They did rally Z cars you know, in 2wd...
http://www2.zhome.com:81/History/rally.htm
It sounds like all you want to do is build a car to wail on in a field. If that's the case, you could put an LSD in it (or weld the diff) and be just fine.
We used to play with an '86 Cutlass in a friend's field, with a 305 4bbl and an open diff. It moved plenty fast for messing around in a field, trust me.