Looking for some info on fuel rail test ports.

I am trying to find some information on fuel rail test ports....in old Neon projects, when adding a return line we were able to remove the shcrader valve from the test port and hook up a 4AN braided line as a return line to the tank to the test port...I am hoping that I will be able to do the same thing with my Duratec30 fuel rail I am using. So I guess my question is whether all the fuel rail test ports are a standard AN-type flare, or whether I am going to have a time tracking down the particular flare and thread size. I would think they would all be the same to standardize diagnostic tools, but I dont know.

i think they are, or almost all are.  my efi pressure tester is 4an.  i've done the same on every manner of gm engines and even on the E55 AMG.  pulled the schrader and hooked up a normal 4an braided line to fuel the nitrous system

They are all pretty much the same EXCEPT for Ford 

The ford thread is the same as what you find on a tire's valve stem so you can probably look up the fitting for that pretty easily.