I would just grab a set out of a junkyard for next to nothing....They probably wouldn't help a stock car that much, but I haven't upgraded so I don't know from experience.....You can look on ZZP's website and check out the injectors they sell, I know there are quite a few. But for the money, if it was me I would find some out of the junkyard because with the amount of money you would save, you could use it toward other performance mods
EDIT: Also if you buy the used injectors, while they are out you might want to consider having them ultrasonically cleaned by a shop, not a bad idea!