Eric,
Even though the carb is new, it may not have had the correct adjustments on it when it was installed (just a guess, and trying to help fix the problem with lowest possible $ for you)
I'd just double check the idle/mix screws, and float level, should take about 10 minutes, and then you can rule that out, and go from there. Also, possibly double check your timing. You could be blowing a lot of unused gas out of your exhaust, which could be a reason for the low MPG and lack of power.
Just trying to help out with where I'd start. I'd tend to think though with your set up, you should be getting around 13-16 mpg though, as others had mentioned.
Something to think about though, is to just take it in for a gas analyzer test at a local carb shop. May cost about $50, but with the prices of gas now, you could easily save that by boosting your MPG up from 10!
Good luck with it, and let us know if you figure it out.