Hi Dave,
I think its important to get the correct offset for the rims for the designed suspension set up. This may not be the case with standard ford wheels. Many different tyres fit 7"rims, I seem to recall 235's fit which is what Pilgrim recommend on the rear anyway.
Have a look on this site -
http://www.performancealloys.com/index1.htm
Norm.
Oh well, done it again!