Hi,
I've just found a drawing for the rear stays on the EW - it gives a dimension of 7" to the inside of the lower lugs, and shows dimensions either side of the centreline - 3 1/8" on the RH side and 3 7/8" on the LH side. From this, you should be able to work out the alignment and width across the lugs for the rear wheel.
Regards,
Eddie.