What determined Thompson vs Saginaw steering gear?

Just curious what decided if a car got Thompson vs Saginaw steering gear? After discovering my idler arm was bad and determining I've got Thompson steering components, it left me scratching my head... uzzled:

 

My guess would be availability. Thompson Products used to make top-quality parts. I can remember when Thompson one-piece valves were the ones that everyone wanted for their performance engines,

 

I think you're right John. It's that way with carburetors and brake master cylinders on the '55.

 

Thompson Valve? They helped the Ramo and Woolridge boys to some measure of fame. I used to work for them boys.

http://www.trw.com/