First point, can you sell you current truck and get by till the new one shows up in 4-6 months. Second, shop around a lot. I just got a 2021 in mid August that I ordered end of March 2021. There was a HUGE difference in the quotes from various dealers. I basically sent the exact build sheet to 7 local dealers, 3 never even responded but then kept emailing and phoning me, told them to take a long walk off a short pier. The others there was a $17,000 spread on EXACTLY the same truck order.
With stuff on the lot, I get them not wanting to dicker because they have no supply; with factory orders, it does not reduce their inventory allocation for the current year, it is a free addition to their allowance and it benefits them in furture years with higher base alotments which are calcualted on total through put of previous years. That is why dealers push so hard for fleet deals. Any dealer that does not compete aggressively for factory orders really doesn't know how to run his business. Smaller independantely owned dealerships, mostly rural, will likely understand this best. Let us know how you make out.