I will not state all the differences I know of since you are not in Cali,then you have nothing to worry about with a Cali car.
50 state MAF sensor and 140mph speedometers were all added in 89.
This is being a little more technical but there are different oil rings in the 90's.
Early 90 Mustangs had no arm rest,later in the year they were brought back.
As stated airbag in 90 no tilt,also the running horse logo introduced in all 90's.
Another technicality phosphate coated gears in the T5 tranny in 90.
In 91 bigger fenders to accomadate the new 16 inch Pony wheels.
In 93 one solid color they got rid of black trim they had on the 87-92 cars.
Reason being for the lower power ranking on the GT/LX for 93,and this is coming from Ed Lyons at FRPP"the Cobra had 235hp in 93,the GTLX the year before it had 225,it was all for insurance" the Cobra probably had closer to 255-260 so there is no difference in power between the 92 and 93,there is a mechanical difference 92 had forged pistons,and 93's had er hmm
hyper-euretic or something like that LOL I hate the pistons reason I cannot spelll it. LOL Sorry Unit5 and Sky had to throw that one in LOL.
Anyway good luck with your car when ever you get it,and follow the advice on here,it is all good from what I read.