BMX - BMX hub for single speed road bike

Ok I don't ride BMX, but I'm looking to run a BMX hub on a singlespeed road bike. I posted the following to the singlespeed forum and haven't gotten the feedback I was looking for. Maybe you guys can help! Thanks!

I have a Fuji Feather which I’m customizing. The stock gearing was way too low for me (46/16). Right now I am running 49/16 on it and can still make it up most of the hills where I live. However, I can’t get enough speed on the flats. Taking it up to a 52 would be negligible. I’d like to switch to a cassette hub instead of the freewheel. However with my 120mm spacing, the only option seems to be a bmx hub, with 3/8” axle, and space it out. I don’t know much about bmx hubs though. I found a couple that looked promising (G Sport, KHE) except they have drivers instead of replaceable cogs. Not sure I want to be running a 49/9!!! I’d like maybe 11 or 12. Also I need something that is going to hold up to a lot of torque because I ride hard.

And I realize that Chris King may be my best bet, but not sure I want to shell out that kind of money right now. Just looking for other options. Thanks

This might be a better mechanics forum question ? But here is the breadth of my experience with it. Had to replace a 16T freewheel on a SS/FG bike. I also have a BMX that's 16T freewheel on the back, it's a 2003 and has the 44T up front. Anyway, the LBS had one and the bike mechanic told me there was no difference as far as screwing the thing on between the freewheels, whether it was going on the SS/FG 700C or a smaller 20" wheel. Maybe that was because it was common for what he did that day ? A road bike cassette is a freewheel though or the wheel hub is. And bmx doesn't have a FG 9T that I've ever seen (not to mention the 11T or 12T) ? Those are SS freewheels. Sounds like you're needing a road bike though.

12T ?

http://www.nashbar.com/bikes/Product_10053_10052_199339_-1_202080_10000_202427

http://www.alibaba.com/product-gs/291148743/12_tooth_single_speed_freewheel.html