Well I'm guessing that the 400 is blown out? The 2WD 700 whould work if you got a new tailhousing too hook it up too your t-case, I think you whould have too move the crossmember too, However 6.2's like too eat 700's alive depending upon how you build them, How well you take care of them, Weather or not you have a tranny cooler etc etc. I whould just rebuild the 400 or get a new one myself, It's a much stronger tranny than the 700, And unless you do a lot of highway driveing you don't really need the overdrive gear of the 700 anyway.
Hope this helps.
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