I am not clear what the 120-130ft includes. The tower is included?
The 6 runs of #8 is 3 pos and 3 neg?
Three #8 CU wires in parallel has 0.2094 ohms per 1000'.
AL #1/0 is 0.161 ohms per 1000'.
If the wire is THHN only (not also marked THWN) it is not suitable for wet locations.
Not sure what that means related to the conduit, like does the conduit need to be waterproof?
Pulling 6 pieces of #8 THHN through 125' of conduit will not be the most fun ever experienced.
The cost of the conduit, fittings, and grease for THHN? I do not know.
Last 3 conductor #1/0 AL USE I bought was about $1.30 (IIRC). It does not need conduit. It needs some special connectors and special grease for the connections.
Might find buying AL is cheaper than than conduit parts. Direct burial wire sure would be easier.
Some more here,
http://www.fieldlines.com/story/2007/10/21/15025/959
G-