Can I Use This Wire?

I have a previous post that started off with flickering lights and has now moved on to where I am in the process of making a new wiring harness for my 1965 Dart. I have already made the forward light harness and am about to finish the engine harness. Has been a chore getting the correct colored wire, but I have managed to all the colors except for one. Have not been able to get 16-gauge blue with white stripe wire. Does anyone know where I can buy this size/color wire?
Found some 18-gauge blue with white stripe and was wondering if someone can tell me if I could use this size wire. The wire will have a run of about 6 feet going from field terminal on alternator to VR.