many options mate.

8", 8.5", 9" and 10" widths.

many go for the 8" with no problems.
a couple of cars are running 10" rears.
my car is on 9" with no problems.

but Martin at Reyland has recently had them made as the 8.5" which is possibly the ideal width for an escort cosworth.

what colour is your car mate, may help the wheel colour choice.