What brand R&P gears to use for a rebuild?

Since I'm sort of in the business, let me tell you this; most R&P gears on the market today, regardless of what it says on the box come from 1 or 2 overseas sources and are re-packaged once they get here. Generally the quality control is pretty good, not like it was about 10 years ago. The key to quiet, long-lasting gears is the set-up and quality of the (Timken) bearings used. Gear set-up is one area where the skill of the technician makes all the difference in the world.
Any one of the above mentioned vendors can meet your needs.
I know that Randy's Ring& Pinion (Yukon) has decent customer service and knowledgeable sales people.
......no, I don't work for them.