on hybrid honda's write up, there is a picture of the r countershaft with the 5th gear installed. there is a gear that came off of the stock countershaft, about 1 inch wide, with shallow straight cut teeth that doesn't seem to fit anywhere on the new countershaft. anyone that has done the final drive mod, interested to hear from you. thanks.

 

don't know about the install.. but great mod! good luck..