Just take the tranny apart and do the following:
- Install the forward-only-conversion kit. This will greatly simplify the transmission and make it stronger. Plus, it'll weigh less.
- Remove the first gear. It's the largest one. You won't need it and it'll further reduce weight.
- You can do this mod, which has worked well for me, or you can use b0gh0s' adaptor thingy.
While you have the tranny apart, you might want to decide if you want to go with the narrow or wide ratio gear sets. Actually, since you remove first gear, there is no "ratio" anymore, but the second gear reduction ratio does change.