about to replace my ignition barrel with a start switch, has any one got a diagram of what wire does what on on the sierra barrel?

I didnt have one...

Just use a multimeter and work it out

just being lazy

Can you not work it out from the Haynes Sierra wiring diagram??

http://faq.ford77.ru/pdf/sierra/0903-wd.pdf

Red permanent live
Black yellow switched live/auxiliary position
Black blue cranking feed to solenoid

pic