if I recall correctly, the GW arm length is adjusted (lengthened) to compensate for the lower than stock mounting location to keep the spindle more or less in the stock alignment .... the GW drop is 1 3/8" (memory getting old here, but should be close) .... so using the Shelby 1" drop holes may push the spindle outboard a tad (i.e., increased camber angle) ... but since you'll need an alignment anyway, it can be adjusted out .... but I would guess that the changes wouldn't be severe enough to worry about because we're talking fractions of inch here ....