I'm putting a 1958 3.4 engine from a Mark1 into my 1967 340. My car had a funky aftermarket ac installed which is not going back in. My question is will the crank pulley on the older engine work with the 340 power steering / generator setup? First shot shows the early pulley. second the later on the engine that I'm not using.

 

That early MK1 pulley uses a single V belt whereas the engine you have removed had the dual V belt.
I would be looking at putting the later dual V belt pulley onto the MK1 engine particularly as there is a fairly high load on the belt system with the generator/power steering pump.
I doubt whether a single V belt system would be adequate for the job

 

This the front pulley on my 3.4 1967 S Type Engine that has power steering just before I removed it during the rebuild. It is basically what you have in the second photo with the balance resonator attached so I would use this one.

 

At some time in the history of the compacts the crank pulley was changed from alloy to steel.