I bought a couple of pairs of target stocks that need to be restored. I don't have them yet, but they are non-diamond, k-frame, relieved; and not too worn. Are there any youtube or other how-to instructions out there?

It's not hard to refinish them. An old tooth brush and mineral spirits will clean them up , scrub and let dry , repeat if needed.
When clean and dry, sand any rough edges smooth and apply a finish.
I have tried many finishes over the years and my favorite is Minwax Tung Oil Finish, I like the way it goes on , dries to a non tacky surface and the way it looks. True Oil is my next favorite.
If pieces of wood are missing, that envolves a bit more work.
Gary

How to- Grip / Stocks Refinishing with photos! FINISHED!

Go to this thread right here on the forum. It's really instructional and intense but you should be able to get some good ideas from it even if you don't follow it completely. When you get them done, post some pictures.

TruOil is a good product that I've used for many years. Bob

I have been using a spray on stripper, seems to work good in the
checkering. Take whole mess off with Mineral Spirits and brush
with natural bristles. Do a little dent raising with steam if called
for. Sand and finish with Tru-oil, 4 or 5 light coats. To thick with
Tru-Oil and it wants to stay tacky. Make sure you buy your TruOil
from big store that has good turnover of stock. Birchwood Tru-Oil
has shelf life even unopened.

Tha factory had used three types of finishes over the year.Oil rubbed ( flat ) Lacquer ( gloss ) and Epoxy ( semi gloss ) Tru Oil can only mimick the first two,you would need an epoxy semi gloss finish ( think tool handles) to recreate the last option.