This is the helper spring set up on my '40:
Helper spring 1 Helper spring 2 Looking at my '41, I think they would fit either '40 or '41. I don't know if they are aftermarket or original but I have seen identical ones on eBay from time to time. Eventually I plan to go to an open differential an eliminate them on the '40. If you have trouble finding something that works well for you, send me a PM via this forum and I may be able to help.
Joe
