[klr toy]

I've been looking into doing this conversion also. I looked at a wrecked limited today and the part# for the amp is 88650-0C070. The part # in my 08 crewmax is 88650-0C050 also. I also made a list of all of the wires in the J19 connector and compared them from the manual to the auto system. The only extra wires are for the 2 previously mentioned sensors- 4 wires in total. I went and ripped the dash out of my truck and looked at the existing harness to see if in fact it was prewired for these circuits. The wires are in fact all there and in the correct locations so that is a good thing. It would appear that the amp needs to be replaced, but you won't have to modify the harness.
One thing that nobody has mentioned here is that the amp will most likely need to see the extra damper servo motor on the upper part of the manifold in order to work properly. I have to look again to see where the connector is for the servo motor. It may have to be added as well. I can only assume that every component will need to be plugged in or the system will go into some kind of default limp mode. I plan on getting all of the components from the wrecked limited that I was looking at today. The only crappy thing is that the wrecker is super expensive and will most likely make me buy the whole heater box as an assembly. It looks like the damper can be added to the existing box, though. There are mounting points for the motor on my heater box already, I'm just not sure if the flap can be added without removing the whole unit. Even though it may cost me $600 to get all the parts, it sure beats paying the extra 10 grand at the dealer!