1991 Electronic controls??

[Two Many Diesels]

91,, 2500 with 4L80 (I think) Is there an electronic controller for the 4spd auto??? 4spd would be nice with 4.11 or 3.73s???

[More Power]

Yes, the 4L80-E, in its introductory year of 1991, did indeed require an electronic control module.

https://www.powertraincontrolsolutions.com/ sells aftermarket kits that make it possible to install a 4L80-E into a non-electronic vehicle... not exactly cheap, but good stuff. Some have adapted the wiring and TCM from an older vehicle, but it's harder to do though a lot cheaper - when you can find the parts.

Analyze your towing requirements, which will help you decide what differential gearing would be best for fuel economy and overall vehicle performance.