I came across a very old NOS plate system that only has 4 holes in each spray bar. The male fittings coming out of the plate have a taper on them to fit the female feed line...no place to put a jet. I contacted the NOS tech line and they couldn't find the number that was on the bottom of the plate (02025) listed anywhere. Is it possible that they didn't use jets back then and that the 4 small holes are what is used to meter it?
I've got one of those old plates. Bought it about 1985. Still works fine and has been on a few different cars over the years. It's pretty basic. Just make sure the nitrous bar is on top of the fuel bar, so the nitrous spray hits the fuel and atomises it.
If you get on the NOS site, it shows how to work out hole sizes in sq in's. Then the ratio from n2 to fuel. If you haven't used it, it would be worth checking it out before you do in case someone has drilled out holes.
This is bringing back some old memories of an old Marvin Miller base plate set up I used a few years back, or was it 30 years ago Sandman is right, make sure the nitrous is on top. Drill the holes out to .375" for a 1200HP kit.