One of my previous combos WAS 2.45 cogs with an OD 833. I was trying to eek some mileage out of my tired 360 with a Summit/SSI 204/214 cam. It made no better mileage in OD than 3rd, although it did lug down the road at 65-70 OK. Basically had to downshift every time you needed to pass, though.

Clair