Power window regulator spring
 

I have a 1988 camaro with the original window motors still in the car, my issue is that the windows will not stay up when the car is moving. Both windows go up and down fully, but very slowly, the problem is that when the car is moving both windows start to lower about 3 inches or so. I plan on replacing both motors but i am wondering if the regulator springs might also be shot. Has anyone else had this issue? Can the spring be purchased separately or will I have to buy the whole assembly? Thanks for any help.