Car Photographer - Good luck with your new project, it is a nice looking kit.
Sorry for the late response, but I have a 1980 Spitfire 1500 and it is 12v all around.
Even though I am re-using the original wiring loom on my kit, I would recommend the Langy's one.
As it will save a lot of time changing connectors and lengthening/shorting wires on an original loom.
Cheers, Paul.