I generally build by visual reference. If it looks right, it is.
I found this image on the internet:
http://www.motorstown.com/images/triumph-3hw-04.jpgScale down the image to 1/35, then look and measure the cables for scale ref
I usually use whatever tiny wire and solder I have on hand. Another resource might be monofilament (fishing line). This is sold in various tests (gauges)
hope that helped