Welcome! There are a few Bluefire threads here and all are quite informative. Give them a read when you can. I have a 2002 Freightliner and also the 6 pin. I bought a 6 pin adapter but these are hard to find now, so you most likely will have a 9 pin and will need a 9 to 6 pin adapter.
Mine does display transmission temperature as well as selected and actual gear for the Allison. Cruise control, speed, boost, lots of other data points. I think you will be pleased.
2002 Damon Escaper (Sassafras). 3126E Caterpillar, Allison 6 speed.