Not sure where you are getting $500 discount from Tread Lightly. I just looked into this and unless I have old information, joining makes you part of the "FCA Affiliate Program". Then, after 30 days of membership, you are eligible to buy your truck at 1% under Invoice when you close the sale. Dealers want to do this because FCA reimburses them by reducing their cost by your 1% and then gives them an additional 1% off as a bonus for participating in the program.
I just ordered a '22 3500 Limited 4x4 LB CC DRW and my local dealer offered me "Invoice" (he keeps the Holdback). (So glad I don't have to drive both ways from CT to New Orleans to trade my truck in and drive the new one home.)
And, I was going to save another 1% using Tread Lightly.
I worked on an order with my dealer and generated a final POC. A few days later, when I sat with the dealer and placed the order, we found that FCA increased the base price by $200 - from $67,570 to $67,770 and also the former "Delete 20" Wheels" credit (Option 57E) went from $500 down to $0 - thus, increasing the base price of a DRW Limited by $700.
So much for my 1% below Invoice strategy...