I have been getting some mixed information about the fitment of 15" SAAB steel rims to Escorts. From what I can tell, there's 15x5.5 and 15x6. There are two offsets, 35P and 39P.

So which variation is needed to fit a standard MK1 escort with no fouling? Thanks

Not conclusive proof but at least you can see what fits and compare to the SAAB offsets. As a comparison a 12P offset is regarded as the desired offset with a 7 inch rim (on a Mk2 at least).

http://www.rimsntires.com/rt_specs.jsp?item=Wheel-Tire%20size%20comparer&showRim1=1&showTire1=1&sw1=195&ar1=60&bd1=13&rd1=13&rw1=7.0&et1=5&showRim2=1&showTire2=1&sw2=225&ar2=50&bd2=15&rd2=15&rw2=8.0&et2=0&text1=13x7%20Hotwires&text2=13x8%20Compomotive%20MO

Thanks for that link Paul, it's awesome! I crunched some numbers and have found that a 5.5" SAAB rim with 35P offset & 205/50/15 tyres will sit in an extra 10mm compared to a 205/60/R13 tyre on a 6" rim with 26P offset (which I have at the moment and they only just tuck)
So there'd definitely be no issues with guard scrubbing. And as for backspace (including tyre) the saab rims sit 9mm further in than the 13x6 with 205 tyre. Now finding a set will be the hard part..