I put on a set I made and I also had the same problem with the nut not wanting to come off. I used an allen wrench to hold the top of the strut from spinning. Man was it a pain in the ass to get off it was like the two nuts were seized together. It turned both all the way off.

1999 3.0L Cougar: 220fwhp and 200tq 2003 VW Passat W8 with 4 Motion AWD http://www.cardomain.com/ride/300644 PM for intrest in 3L SVT Contours, 3L swaps into your current car, Prepped 3L engines, or anything 3L related.