Wheel information

[deezee]

I've been trying to get some wheels I like, but am having trouble. As I'm following the book and actually building on a budget, I'm trying to get some off ebay. It seems that virtually all Ford alloys (apart from newer cars) will do. But I'm having trouble with the offset. I know the ideal is listed as something like 38-42mm, but on what width alloy? If I get a 6.5" alloy whats the offset meant to be?

The main concern is that the wheels on the back are going to sit miles in from the arches and looks stupid If anyone has Photos and Info of what they have fitted, it would help loads.