Most pocket door hardware, and the prefab kits which include framing, are intended to use standard doors - this can include an existing door that you have. One thing to check is that the door hardware should have weight rating - check that against your existing door as old solid wood doors can be heavy.

Other than that, you can't go wrong with Johnson hardware.

Here is a link that might be useful: Johnson hardware

Thanks for the info and the link...any thoughts on pocket (inside the wall) verses the exterior wall mounting?
I'm going back and forth...obviously the exterior mounting would involve less work, but how do they actualy close and latch? I've not found very good information online. I'd love to get some input from folks who have either kind.

They do allow you to pick up some floorspace, but the space saving has both a cash and convenience cost.

We are used to being able to give the door a shove to open or close, which doesn't work with sliders.

But they have been standard in Japan for centuries, its just a matter of what you are accustomed too [I wonder if/how Japanese teens manage to slam sliding doors...]

A case can be made that sliders are best in areas where they won't be opened and closed repeatedly on a daily basis: great between the dining and living rooms, maybe not so much for the entrance to a bathroom [though I do have a friend with this setup who has no complaints].

As for a true pocket vs. a slider mounted on [not in] the wall: a pocket needs a thicker wall, may necessitate moving wiring or phone lines. The hardware should be trouble free, but if there is a problem, the wall may have to be dismantled to handle it. Not cheap or easy to install, but probably the way to go if you are having the work done professionally. The on-wall kind are usually adapted from sliding closet or horse stall hardware. Much easier to DIY, but they don't 'seal' as tight and finding hardware that looks good may be tough-to-impossible if you want a look that's at all tradtional.

In my remodel (in-progress) I installed pocket doors using the Johnson hardware - the 1500 package - in a standard 2x4 wall. It was very straightforward. The opening has to have a header a little higher than for a standard door. The instructions explain it. There is no room for any kind of outlet in the wall where the pocket door slides into. I bought a cheap HD door & hung it to make sure it worked. Everything was fine.

Awesome! I can't wait to get the project underway! One of the doors will be in a new wall, so it will be easy to install it inside the wall, and the other will be on an existing wall, so I think I'll go with the exterior instalation on that one.
Thanks for the input!