I recently picked up a beater Pentax 6x7. I have the 105mm lens (in bad shape).
I'm trying to decide what lens to ad for portraits. I'd like to be able to do head shots.
The candidates:
135mm f4 macro. Slower than I'd like and I'm concerned about f4 both for the light and the dof. On the plus side, it'll get close as it is.
150mm f2.8. I'll need an extension tube to get close. f2.8 is nice. I see less about this lens than I do the 165mm and they seem to go for less. I'm wondering if it is as good as the 165mm.
165mm f2.8. Again, I'll need an extension tube and I like f2.8. I see this one recommended frequently. What does it have over the 150mm f2.8?

Anyone with experience with these lenses that would care to share advice and examples?