8&3/4 489 Cone Style Mod

Trying to find an article from about 20 years ago or if anyone knows how to do the mod or what part was called for. My dad had modified one of our 489 cone style pumpkins from an article out of either Mopar Muscle or Mopar Action. He had the face machined like you would expect but it had you modify the springs. It told you to get a certain transmission spring and you put it inside the other springs making a double spring so more pressure was applied.

It remember it worked great but he has looked all over and can't find it in the magazines he has saved and we have another one that is slipping and needs machined and shimmed and we want to do the spring mod as well.

If anyone remembers this that would be great.