APE idler assembly question

Perhaps Jay will chime in and provide an answer but someone else might know...

APE sells a solid looking cam chain idler assembly. Will it fit EITHER a 903 (73-77) or a later model KZ1000 (79/80). Their idler assemblies are different and the number of teeth in the chain is different. I was wondering if the two types of bikes needed to have different amounts of reach to put tension on the chain or it was the same. I am going to look at different idlers up in the shop after lunch and will see if I can figure it out but I suspect Jay should know this off the top of his head...

In other words, can an idler from a 1980 MK II engine fit on a 1973 Z1 for instance and vise versa???