[ QUOTE ]
[ QUOTE ]
Should be the 4L80 transmission, 4 speed w/OD based off of the TH400.
[/ QUOTE ]
91 should be the old body style still if its a 4 door. 91 duallys had the option of a 4L80E?
[/ QUOTE ]
Yep, 1991 was the first year for the 4L80E. The gas engine ECMs controlled them and when behind the 6.2 it has it's own stand alone ECM, which is very desirable. IIRC of course.