2t2 crash;
I use the wiring from inside phone wire. It is pre-coloured, flexible, yet holds its shape. I buy an extension or replacement phone receiver cord from second hand shops or from Wal-Mart or other cheap store. The exterior rubberised housing is cut easily with scissors or a hobby knife then just pull the colour required from the inside wires and cut. I use superglue to hold the wire in place and drill an appropriate size hole to accomodate the gauge of wire.
Incidentally if you look through the Kalmbach Catalogue of Modelling References on the FSM page. You will find a great reference book in the Scale Auto Detailing book for sale there. In the book is a list of wire sources and gauges to use for type of representation (i.e. ignition wires, plugs etc) as well as some really good references on detailing motor types.
There also is an article FSM published awhile ago (exact location escapes me) on detailing the 1/24 Willys Jeep including a detailed description and photos of the engine.
Best of luck with the build. If you need further information let me know.
Cheers;
Gregory