I just used plastic wire loom for the several wires I needed to run: rear
wiper, oil pressure gauge, oil temp gauge, tach, cold start valve, etc.
Put some extras in the bundle for future use; I was glad I did, as I had
some later ideas and didn't have to run separate wires.  There's enough
to cable-tie to, and you are running through protected enough spaces, that
I don't think fancy conduit is needed.  Making up a neat harness with
heatshrink tubing is probably the classy approach, but you'd need to in-
stall, trim, remove, heatshrink/tape, and reinstall.  This process is
on my good intentions list, but needs to wait until I lose my job.
B.