Supermatic trans controller
 

Required when using a GM electronically controlled automatic transmission in these older trucks with carb motors. Includes wiring harness, software and connector for laptop. Controller allows full programming of shifting, as well as part-throttle, wide-open throttle and shift firmness control.

These are about $1400 after tax looking to get $1000 obo shipped for it. Brand new never installed only opened the box to look at it.

More info https://www.gmperformancemotor.com/parts/19212657.html

http://i.imgur.com/YlZcgzJh.jpg