Now for the tricky part!
You need to remove the heater box from the truck. I didn't want to remove my hood, but you do need to unbolt the 2 back bolts on the hood hinge and can gently tip the hood forward to get enough room to get the heater unit out! I put a line on the fender to mark where the hood needed to go so it would line back up when I put it back on. Don't forget to put your hinge bolts back in before you close the hood!