wow... i dunno how you got the valve springs outta that, but im positive he was referring to coil springs, mostly because thats what he stated
my answer: if they fit, the ride would be higher (2000's are heavier than a fox mustang, so putting those spring would raise ride height) and the ride might not be as nice, considering the 2000 springs are made for a much stiffer chassis (considering you dont have SFC's yet)