Just got done installing the H-D oil cooler (#26155-11) on my 2011 Ultra Classic. Took about 2 easy hours. Made sure to cover the front fender to safeguard against nicks and dings. Got the 1/2 in. socket with 7/16 in. hex bit needed to install the oil filter adapter from Grainger, pricey, but a must have for properly torquing down this part. Used a skin coat of black RTV on the gasket of the oil cooler adapter assembly. Some other needed tools are a 7/8 in. socket and extension to take out the original oil filter adapter and a 7/16 in deep socket to loosen up the voltage regulator so that the chrome cover can be fitted onto the oil cooler. Also need a T-45 torx bit for the oil cooler bolts.
If you have lower fairings like me you'll want to remove the left one so that you have room to work. Three bolts gets the fairing off with a T-40 torx bit needed for the bottom bolt.
Much easier to install the new oil hoses onto the oil cooler before bolting it onto the frame. Orient the hose clamps so that you will easily be able to get a screw driver or socket onto them when mounted on the bike.
I only lost a very small amount of oil when removing the oil filter so no need to drain the oil prior to install and I could have reused my low mileage oil filter, but I dented it while twisting it off with a belt oil filter wrench. I bend an old x-ray film to form a catch under the filter so that any oil draining out when the filter is unscrewed gets routed out and down to my drain pan instead of dripping all over my frame and motor mounts. Fired up the motor and no leaks were seen so my next project will be to install the H-D oil temp gauge.