What I got back from the dealer today "I checked with my general manager this morning, and he knows for a fact it can not be changed. Another one of our sales guys had a customer who loved the build we had on the Avalanche gray Raptor but wanted it to be an extended cab and we couldn't change it so he didn't go with it.
He's going to try to get me the vin today on it. When it comes to the tailgate appliqué I'm sure you can get that through parts or online, the other options aren't as easy like you said. There are places that do heated seats aftermarket in our area though. The tailgate step is built into the tailgate so you'd of course need an entirely new tailgate."
So I guess they can't change it. I might be able to buy one from another member and trade. Tailgate, paint, & applique would get expensive. I will not be sitting in the back seat so I'm ok without heat. Everything Ive seen on here says it can be changed, but guess they can't or...
If he is going to get you the "VIN today" then sounds like it may be scheduled for production. If still shows in dealer's system as Unscheduled Clean, then you can make changes. I did one change in December and two more last week.