6-speed manual

I was wondering if anybody has or has driven an 8.1 with the 6-speed manual tranny. I've never seen an HD with a manual tranny so I'm guessing there are very few out there, except maybe WT's. My 6.0 in my HD does allright, but I may consider trading up to an 8.1 with a six-speed manual. With 3.73 gears do you think it would get similar gas mileage to the 6.0/4.10's? I've driven several 8.1's with allisons and they seem to have alot more pulling power. I just don't drive enough miles per year to justify the diesel option. Does anybody know what percentage of HD's even have a manual tranny?

Seems strange to me that an HD would have any need for a 6 speed transmission.