Eldorado2k,
When I went looking for my vac at both Sears'(Craftsman), and then HD(Rigid). They seemed to have any attachments you could possibly need to make any transition.
My Mom actually had a brand new Craftsman that she never once used, and just gave it to me, which was cool. And after going and buying a detail kit from sears for it. I also was able to be numerous other attachments from HD. All fit universally for me.
The hose my machine came with was a 2" + something hose, and I was able to transition it down easily to 1" something. I am very sorry I don't know the Exact diameters off hand. But I know that nearly every scenario I put together, they had some kind of fitting to make it all work.
Mine's a 3hp, and it's all I probably need, but I would like to step up with a more powerful suction soon.