There's alittle more to Honda trannies than just popping gears out of one tranny, and throwing them into another. Besides the matching of the FD ring gear to countershaft, and the cable to hydro gear & issues, every B series tranny is shimmed differently, and you have to know where to check the gap. failure to shim correctly can cause the shift rings to not properly engage a gear while shifting...causing gears to dis-engage "pop out", or the dreaded grinding gears syndrom.
I would find someone who has "no shit" done it! I'm sorry, I would, but I'm still out of the country, so I can not.