Look at www.carfolio.com. They have loads of stuff including track widths for various cars. Remember that track width is usually the width between tyre contact patch centers and thus is sensitive to the type of wheel fitted.
I am virtually certain that the escort axle will not be wide enough for the +4" chassis since it barely fills the arches on a standard width chassis. Better to go for a Capri (+2.5"
or even better a Cortina (+4" axle otherwise you are likely to have the problem where your wheels
will foul the trailing arms. You could use spacers (and probably still will with the Capri axle) but better to minimse the use of spacers and I
certainly wouldn't go more than 1" on the spacers per side. So Capri axle with 1" spacers each side or a Cortina axle with no
spacers. One other thing, I think (from another post here) that the Capri and Cortina axles can swap diff's and so you could put an LSD from a Capri into a Cortina axle if that was a concern. Note that I am not an authority on Ford bits so check this swapability first!!
I hope this helps,
Craig.