Ohtsu makes the prowedge, you can get them from chapparal. the 13/41 would be good, but might not be good for trailriding with some smaller tires. It would give good acceleration though, its also up to personal preference. I know from my experience, first gear is almost useless in most banshees ive ridden. Even in our heavy modded banshee geared for 1/8 mile i have to shift to second almost immediatly. In dirt drags, unless u got an override and you are hooking up real hard, 1st gear is totally useless.
Everything aside, if you really want some improved times at the track, get some pro wedges over them razrs. If you must leave in first to make trail riding better, go with as much gear as your motor will pull in first so it doesnt make 1st gear totally useless.