windows fail and fall - need help to make sure I get the correct parts for replacement

I can't find much in the way of markings but the double hung windows that I'm having issues with are both 36"wide x 48" tall and the windows weigh in at 16#. The pivot shoes split at the bottom and fall out causing the window to drop unsupported by the coils. I'm assuming that I should replace the coils as well as pivot shoes. The attached photo is from a 24" wide window (issue does not happen with any of the smaller window frames) - the problem windows all have one coil spring just like the smaller ones. The window channels measure 7/8" deep x 1 1/4" wide and pivot shoes are 13/16" wide x 1 1/2" tall. Please recommend replacement part numbers. Thanks in advance for your help!