Have you tried local parts places? Most of the time they'll carry the same parts cheaper. I've always been able to beat NPD prices on suspension parts and never had to worry about shipping or quality. I stick to NPD for the mustang specific stuff I can't get anywhere else. I'm seeing $72 @ partsamerica.com (advance). I suggest checking a NAPA, PAPA, or whatever good parts stores in your area.
Otherwise, I doubt the quality of the american pony part will be much, if any, less. However, I like brand name parts like Moog for suspension, if there is ever any doubt. In the end, would you think the $20 saved would be worth it if the cheap part failed and caused you to lose your steering? Go for brand name & warranty (it's easier to return a part under warranty locally if there is a problem, than to have to mess with shipping the parts somewhere else)
Hope this makes sense. Good luck!