My 150 and 210 will cover 5x7 already, I was looking for something along the 35mm/35mm for the 4x5 that would still be useable on the 5x7. I don't have the 5x7 running yet, still working on lens boards and all that sort of thing, just trying to keep my future options open. So, what does a 120 mm work out to on 4x5?
I've got a 20 somthing, a 26mm and a 35mm for my Nikon F, only use the 35mm, just never find the RoungTuit for the wider stuff even when I say I'm going out to shoot one lens. Somehow the 135 ends up in my pocket "just in case", and it's another example of a tight cropped short tele day.
I'm not quite clear what sort of angle of view you want (I think there may have been a typo on the "35mm/35mm" phrase.), but based on the context, I am assuming that you are saying you want a lens for 4x5 that feels similar to a 35mm lens on a small format camera (24x36mm format; your standard 35mm film frame).
I personally call 180mm normal for 4x5. It closely matches the horizontal angle of view (AOV) of a 50mm lens on 24x36mm format (though it has a wider vertical AOV). Thus, on 4x5, a 90mm (half of 180mm) is very close to what a 24mm lens (about half of 50mm) is like on a small format camera. A 35mm lens is approximately half way in between 50mm and 24mm. So, a lens with the same AOV on 4x5 would be about half way in between 90mm and 180mm: 135mm.
Other people call 150mm normal for 4x5, based on a diagonal instead of the wide dimension. In that case, 75mm would be close to a 24mm, and halfway in between 75mm and 150mm would be about 112mm. Since the 110mm Schneider XL is so expensive, that leaves you mostly with 105s, 115s, and 120/121s to consider.
As I mentioned a few posts back, 120/121s are quite wide on 5x7 film; not similar to a 35mm lens on small format at all. A 135 would be a little less extreme of a wide, though I haven't used on on 5x7, so I can't tell you what it "feels" like.
Now, if you want this same AOV for 5x7, here is one way to go about figuring it:
You know what 4x5 lens is closest to a 35mm lens on small format on the horizontal dimension: a 135mm. To get this same horizontal dimension on 5x7 is easy. You just scale up the dimensions of 4x5 to either the horizontal (7 inches) or the vertical (5 inches) dimensions of 5x7 format, and then multiply 135mm by the factor you used to do the scaling.
For instance, for matching the horizontal dimension, I figure it like this: What must I multiply 5 in. by to get 7 in.? The difference is 2 in., so what portion of 5 in. is 2 in.? The answer is 2/5, or 40 percent. So, 140% of 5 in. equals 7 in. Therefore, you can multiply 135mm by 1.4 to get the focal length that will give you the same horizontal AOV on 5x7 film. 135mm x 1.4 = 189 mm. Your common choices are a 180 if you want to go a little wider, or a 210 if you want to go a little narrower.
For the vertical AOV, you can follow the same procedure. It is easy head math to figure out that your factor in this case is 1.25. (4 in. is multiplied by 1.25 to get to 5 in.) So, you need a 169mm lens to match the vertical AOV of the 135mm lens on 4x5 format. Go down to a 150 or up to a 180.
Almost exactly halfway in between 189mm and 169mm is 180mm, a commonly available focal length. It would look like a 35mm small format lens when used on 5x7 film, and would look like a 50mm small format lens when used on 4x5 film.
This being said, I would say that since you already have a 150 and a 210, getting a 180 might be silly.
I'd go for a 135mm based on what you want. I can't name one off the top of my head that will work on 5x7, but I am sure that someone here can.
P.S. Two helpful Webpages:
1. AOV calculator (open the same page up in two different tabs to compare angles of view between formats):
http://www.mat.uc.pt/~rps/photos/angles.html
2. List of many large format lens specifications posted at Graflex.org:
http://www.graflex.org/lenses/lens-spec.html