sub service feeder

[Ellement]

We have a remote garage that needs a small service entry (240v @ 40 amps) and the main service panel is in another building 100 ft. away. There is no way to run the cable under ground so we have to go overhead. We now have an exterior service wire that has 2 # 6awg with a messenger ( bare braided wire ) that the owner wants to use.
My question is that I know that being a sub service off an existing panel that we need to run separate ground and neutral lines so as not to create a parallel return path to ground, is there any way we can use this existing line we have, or do we need to have a third jacketed #6 awg travelling with the other pair and the messenger (3@ #6 + messenger), what about CEC 10-208(a) overhead sub feed with a acceptable grounding electrode, can we utilise this with his cable using insulators?
Is this service run we have (2 jacketed #6 and the bare messenger) considered a duplex or a triplex run?
Thanks.

[bigrockk]

Hello Ellement,
I believe you should have no trouble using the the cable that you have,it is considered to be triplex.(Neutral Supported Cable)
Use the bare conductor for the neutral.Drive a ground rod at the garage for grounding, 10-208(a)
Also check out rule 12-318 and section 6
You may be required to use a combination panel and not a sub-panel.