Perspective distortion is a matter of distance from lens to subject. It doesn't matter what film format, provided the same ratio, e.g. 1:1.25. It doesn't matter what lens focal length other than acquiring the desired angle of view. For head-and-shoulders portraits most folks seem to prefer 2x-3x focal length so for 135 film, cropped to 1:1.25 ratio, thats a 85-135mm lens. For 4x5 format that's a 300-450mm lens. This is if the subject is framed closely and the image isn't cropped during enlargement. Of course, this begins to become impractical fairly quickly so one will probably need to compromise much of the time.
Regarding print viewing distance being a major factor in how one lens focal length appears vs. another: My personal opinion is that's largely bunk. I don't care how closely I view a print (within reason) of a portrait taken with a lens that's far too wide the image looks distorted.
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