The new z-axis base was installed and commissioned this weekend. The new base pieces are working fine and the printer is looking less cluttered with the old wooden motor supports replaced (more info about the old configuration here). Only one motor is doing the work now with a belt connecting the 2 vertical threaded rods; left and right won't get out of sync anymore.
A small reconfiguration was needed for the software since the motor has an 8 tooth pulley and the rods have 20 teeth. I still use standard replicatorG software; changing the following line in the machine.xml file from:
<axis id="z" length="200" maxfeedrate="100" scale="320"></axis>
<axis id="z" length="200" maxfeedrate="100" scale="800"></axis>
did the trick.
The printer looks like this now: