This is the schematic I used (no accommodations for vintage air though). I used (1) 40 and (1) 10.
As far as the Fan 1/2 vs Low/High nomenclature, Fan 1 means low temp trigger (both fans half speed), Fan 2 means high temp trigger (both fans full speed). C1 (blue) pin 42 should be low temp trigger and C2 (green) pin 33 should be high temp trigger.
How do you know that your fans are only one speed? I don't know that I would call my fans "2-speed", they just run half speed because when Fan 1 wire sends a ground trigger, each fan only gets 6V so they only run half speed. When Fan 2 wire sends a ground trigger, each fan gets 12V so they run full speed.
I don't have a good understanding of the schematic, I just know that it works.
I can't tell how you want your fans to function. If you want them to run like GM designed and how most people recommend, use the schematic here. I like this because it cools across the whole radiator all the time and your fans should last longer and it's quieter.
If you want one fan to run full speed when coolant reaches low temp and the other fan to come on full speed when coolant reaches high temp, you can simply use Fan 1 (low) and Fan 2 (high) to trigger each fan through its own relay and fuse.
Trigger wire size doesn't matter, it's just a ground. The wires that came on my cheapo fans are probably 16, but I used larger wires in my fuse/relay block so I can use higher powered fans down the road. I used 8 to feed the buss bar, 10 to feed the fuses and relays 1 & 2, 14 to feed relay 3, then 14 to feed the fans.
