for a short tele on an exakta, can't go wrong with the steinheil. I have one, it works.
On the body, its going to be very close on the inside to a VX, probably only minor differences. what it isn't like is any japanese camera on the planet! Lots of people that have done shutter jobs on japanese camera get shocked when they get the bottom off an exakta.
The stuck lens, first things first, get a little bit of lighter fluid in it. That should loosen up the grease, but its going to migrage into the apeture and onto the glass pretty shortly after you do that, so you will be tearing the lens down. Scary at first, but its actually very easy. Its 4 elements in 3 groups, childs play and a great place to start learning some repair!
Btw, those meter prisms, if working, are a pretty good find.
Myself and another local shooter have dared eachother to shelve all our other 135 slr cameras and shoot only our exaktas in the comming year. For both of us, that means giving our cameras a CLA, and in his case, a fresh set of curtains. (I think mine will probably survive, if they don't, then he can do mine too!
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