Yes you can switch out your 2 speed transmission for a single speed. All that you would need is one of the 2 single speed transmissions and a single speed clutch bell.

05126 comes with a 44t spur gear
http://www.redcatracing.com/parts_se...lt.asp?q=05126

02126 comes with a 42t spur gear.
http://www.redcatracing.com/parts_se...lt.asp?q=02126

Single speed clutch bell
http://www.redcatracing.com/itemdeta...p?partno=08011