5549 is the only bus I can remember with the tranny upgrade. I'm sure there were others, but MSBA didn't get them. Originally, there were about 50 Blitz rebuilds, and several retired RTS's. The transmissions I liked the best were in the '78 Flx NewLooks (the Selec-Trac). Those were MSBA's high 800 series.
You may have a point - by that time they were already all gung-ho to make the transition to CNG, so I'm sure they were trying to expedite the fishbowl's demise.