If you choose to make this modification, it helps if you have access to a person who has done the modification previously. As for me, it took substantially more than 8 hours, as I found that there is some variation of the dimensions of the after market parts. Perhaps I received the kit for a 350 rather than the 500, I don't know. However, on my kit (Silking from India in a Royal Enfield Package) there was a discrepancy in the depth or length of the bushing for the bell-crank. As a result, the bellcrank did not extend far enough into the inside of the gearbox. This resulted in excessive slop and it being nearly impossible to get the shifter ratchet adjusted so that it wouldn't give false neutrals. Finally, after about 2 months of fiddling, someone on this board (who I still owe a case of beer) suggested I install a few washers (spacers) on the bell crank shaft and add spacers to the detent plunger nut. This made all the difference, I can now get it into the correct gear first try.
It helped to have the Snidal manual, however, Snidal did not mention any fitment problem with aftermarket parts. If you need any long distance advice, post it to this board.