1994 Caravan transmissions interchangeable?

Are the 3-speed and 4-speed transmissions from a 1994 Caravan with the 3.0 engine in any way interchangeable? I ask because the 3-speed in my brothers Caravan is shot and someone offered me a working 4-speed also
from 94' Caravan with a 3.0 engine. I was thinking since it is the same van and same engine somehow both transmissions must bolt on the same way. Or is there a lot more involved in this than I am thinking of? Thanks in advance.
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On Wed, 14 Apr 2010 15:35:15 -0700 (PDT), Sara Brown

I wouldn't say NOT interchangeable, but definitely not a simple job. The 3 speed is not computer controlled. The 4 is. The 3 speed is a more robust tranny.
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