Virtually any servo will work with any RX as long as the plugs are the same size. Some micro servos have smaller plugs.

As for The RX's, as long as the Hitec RX is set up for the same modulation (AM,FM) and the same shift (Positive, Negative) and on the same frequency it should work. Use a Hitec crystal in a Hitec RX. If you are ordering a new RX just tell the clerk what you are working with and they should be able to match you up fine. Hitec makes RX's that will work and those that will not so get the correct one. And order a RX with sufficient channels of course. Also be sure to get a "full range" RX.