So I'm in the middle of a full rebuild, which was initially prompted by shifting issues where I thought the infamous spring broke. It appeared to be intact but something else was going on. In any case I'm rebuilding a five-speed transmission that's an early 75 version, before the September cut off for changes. 

It's now come to my attention that there was an upgraded shift kit that works on this era 5 speed, which has both cams for the shift mechanism with it as well as new arm etc, but I can't find anyone other than eBay sellers who have one of these in stock. Looking at the change, the only thing that's obvious is that the primary detent cam, BMW part 23 31 1 231 611, is definitely different than mine which apparently is the original design with flat tops to the cam sections. That new part above the upgraded version has pointy sections, for much more definitive shift positions. 

I get how this upgrade works with that cam- but my question is, does it have to be replaced along with the other cam in a designated kit? It doesn't look like the other cam actually is a different profile from studying pictures on boxer2valve's site, who has good pictures of the differences between the two versions, but also no longer carries it. Max BMW carries the individual parts, and I would be willing to swap out the flat-topped cam I have in my transmission with the upgraded version, but I would like to know if that single cam with the number above can actually just be swapped out by itself with none of the other parts changed. My cams are in good condition, but I'm not sure if any kind of radius of the other cam is slightly different to match anything to work correctly. 

It's very expensive to replace both when I only think I need one but I'm not sure. I also have the original 15 degree helical gears throughout, and I'm going to be replacing all of those with the newer 17.5 degree versions, as well as likely a new shift pawl shaft just for shift smoothness. My helical input gear has some gouging and the 2 bump follower underneath is definitely worn. I'm going to be taking everything apart with a Kukko 17-A kit, replacing all the bearings etc. 

The only thing I'm not sure of, can anyone comment if I can just replace that single cam? In the old upgrade kit, is that the only part that's actually different from stock as far as I can tell?

I've looked for a while across the internet and these forums for any clues but haven't found anything definitive.