If you are not in a big hurry, which for maintenance items, generally you may not be, you might want to just keep an eye on the classifieds here and other places, people often buy stuff, and sell the truck before installing, or blow the engine, etc.
I get as much stuff as I can this way, I'm real cheap, and patient, I paid 200 for brand new Delphi injectors, which included shipping...
1994 K1500 Silverado ext cab short box
stock L56 6.5 TD, F intake, 4L80E, 3.73 gears
10149599 block, D-Tech PMD on 5288 pump
Goodyear Wrangler silent armour 265 75 R16 E Pro Grade
Bushwacker fender flares
410,000 km