Start scouring the internet and other dealerships outside your immediate area.
When I purchased our 08 F250 new, I test drove one locally, but the dealer wouldn't reduce the price. I started searching the internet. Ebay is a good source, you can see which dealers seem to be offering good discounts or have large inventory and then search their dealership website inventory listings. Use the "completed Listing" function under ebay. See which trucks haven't sold as well. You don't have to buy through ebay, but it is a good source to find larger dealerships that offer what you want.
I bought our 2008 F250 Diesel king ranch new at a dealer in Houston. Sticker was $58k, I bought for $36k. The truck was delivered to my house in Savannah GA on a car hauler about a week later.
Buying a vehicle has never been better or easier. Every dealer in the country can be "local" because of the internet. You know what you want, you don't need to test drive the vehicle since you are buying new. Shipping a vehicle runs around $500-$1500, dealers have agreements with their shippers, so negotiate on this price too.
You might find what you want looking through dealership inventories in markets that are more truck oriented like Texas. If you really want the year end discounts but have specific requirements, start looking outside you immediate area.
I hope this helps.
OJ