It depends on the CB you have now. If your pushed all the way to edge of your engine mount slots, then the larger spur won't fit.
I had to grind my chassis a bit so the upper engine mount bolts and starter housing didn't rub on the TVP running 16/49. I'm running aftermarket tvp's though, so it may not be the same with stock. The extra two teeth on the spur cut down my slipper over-slipping problem a lot though, so it was worth the effort for me.