The 105 is a one-of-a-kind lens, you'll be hard pressed to find anything faster for 6x7 negatives that only costs less than $200. However, I think most people look over the latest 90/2.8 because of the 105. The original 90/2.8 leaf shutter was an okay lens, but the latest version seems really super. The 75/2.8 is really my dream lens, I think it might be a little closer to your 40mm equivalent but it's rare and expensive.
I use the 6x7 and have looked at a LOT of photos from the 67 and 67ii...they are identical (the photos I mean). Obviously the ergonomic and electronic advancements in the ii are nice, but not necessary. If I had that much money to put into a camera body, it would be the Mamiya 7 where the different type of viewfinder will likely help your composition a lot more. And I feel like the 80mm on that is a lot more like a 40mm equivalent.