Okay dentside guys...

[Evan's f250]

(1978) BODY code SD4: SD = Red all Vinyl-Bench Seat-Explorer // 4 = Ranger Cab w/Styleside Pickup Box.

Since 46 is not a special order number, your truck was not a special order. 46 refers to this:

DSO code 46: Indianapolis IN Ford District Sales Office, where the original selling dealer ordered the truck from.

If the DSO code is composed of 6 numbers, the last 4 refer to a Domestic Special Order.

Thanks Bill, these two categories werent loading on my computer, thats y i couldnt find them.