I know some people who are going from auto to 5spd probably figure they might as well go for the 'better' 523/568 stuff but i've owned 520/555 and 523/543/568 (yes all 5 of those) and i've never driven a 520/555 and thought to myself "i wish i was driving the newer style trans". I would stick with the older stuff to avoid shifter complications.
I'm gonna be the first and only to say: Why not keep the 767 cam for the turbo build?
Also, if you're going to run any 'not strictly necessary' wires into the cabin may i recommend you extend/relocate the scanner connector into the cabin? I've gotten very tired of driving around with wires routed in through my window and having to be careful not to pinch my scanner cabling with the hood/door. I have my scanner's extension cable semi-permanently routed into my van through a hole i made in the firewall for the express purpose. Although there is a bluetooth datalogger in the works that may remove the need for this.