I'm not sure if there were factory 30# injectors on Mustangs. Because they have twice the numbers of cylinders and over twice the displacement of our beloved B202s, they use relatively smaller injectors (compared to our B202s) because the whole motor works less. That's my recollection anyway.
That said, check out eBay for injectors, there's always some there. The other place I've had good luck with injectors (because of eBay auction snipers, sometimes it's just easier to buy from a classified ad) is stangnet.com - always injectors available there. And when you get the eight of them in the mail, turn around and eBay the other four. Une morceau gateau.
are all the red injectors high impedance? and what kind of impedance would best suit me if i am using this with a 3 bar fpr and lh2.2? do the sizes and dimensions matter as well or as long as they are bosch does it work? Grey area por moi.
Generally, Bosch style injectors are all the same size. They might vary slightly on the tip where the fuel sprays out, but otherwise they are the same. Same connectors, same o-ring size, etc. I think only when you get into Japanese stuff, like Denso, do things change.
Be wary of the impedance - you need high impedance if you are going with stock components. Low impedance will require a resistor pack. If you are going for a mild upgrade, 24 or 30, then stick with high impedance. When you want to get serious, for example with stand alone engine management, or some other EFI tweaks, then you can run low impedance injectors.
Actually, that's maybe the wrong way to think about it. It just so happens that high flow injectors are usually low impedance, so it's not like one goes out searching for low impedance injectors, it just happens that way - does that make sense?