Question: I just disassembled the front brake caliper (dual piston) on my 1974 Ford F250 390 V8.

There was a spring on each of the caliper bolts in between the brake pads. The springs are really rusty and one of them broke in half.

Looking on O'Reilly's site, I can't find replacement springs. Are these in use anymore? If so, what are they called? Where should I look for a new set?

Answer: 
I'm going to say yes, you should replace those springs, especially the broken one....

Some [Googling](http://www.google.com/search?hl=en&rls=com.microsoft%3a%2a&biw=1259&bih=773&tbm=shop&q=1974%20Ford%20F250%20brake%20caliper%20springs&aq=f&aqi=&aql=&oq=) indicates that springs fitting your description are still in use and you should be able to mail order them.
Your local NAPA store can order them. It is part number UP 82116A and contains springs for both wheels.