Looks like I had a math error in my spreadsheet! The factory thermostat option is lower than I stated initially- it's coming out to $490, not $560 (again, not yet including brackets).
I've ordered the rest of the parts I need so now it's a waiting game, but I will keep you all updated!
And agreed on the above- the importance of ducting and fender well protection are not lost on me. I just want to get the core successfully mounted up first, then I'll work on the ducting solution.