Here is an image with the different types of injectors. It looks as though the brown top injectors you are talking about are 36 lb injectors, meaning they can flow 36 lbs of fuel per hour at the stock fuel pressure. I don't know what the fuel pressure these were rated at for 36#'s, but if you have lower or higher fuel pressure in your vehicle, this will directly affect the amount of fuel which the injectors will allow for a given amount of time. (I am not sure, but believe Ford runs their fuel system at 30psi, someone correct me and I'll update if I'm wrong.) According the picture, these came stock in the 94-95 T-Bird Super Coupe. Note the red ones right next to them are good for 30#'s.

As far as low and high impedance, I found this blip here:
How do I know if my injector is low impedance or high impedance?
You can measure the resistance across the two electrical terminals of the injector. If the resistance is between 1.5 and 4.0 Ohm you have low impedance injectors. If the resistance is between 8 and 16 Ohm you have high impedance injectors.