Is it not just as much the rim width (8") as the offset that gives the problem with 'real' Escort Cossie wheels. The Mondeo 5 spoke ones work because they are only 6.5".

I could get 225/50-16" under the rear arches (and front) of my lowered Mondeo Mk2 LX (FRS engined) but had to use Focus 52.5mm offset wheels to do it.