Hey I've got a quick question for the knowledgeable

I'm doing a 6 speed swap and I was planning on using a R160 rear diff until I can afford to upgrade it but I have just been offered a set of GC8 RA rear driveshaft which I have been told will allow me to use a R180 diff with my SF R160 rear hubs. Is this true? Naturally I want a R180 over the R160.

Another question I have is will I need to use different axle stubs to fit these shafts to a GD diff? Also would Subaru be the best place to get these stubs if I need them?

Thanks for your help.