Yes I have converted many MTH Premier Steam and Diesel loco's to Kadees. I just completed a Atlas MP15DC in which I also closed in the pilot. Almost all MTH hood diesels take a 1/8" shim between the coupler box and the bottom of the cast pilot assembly. MTH F units are quite a bit different.
Just finished a set of MTH F3's ABBAs for a friend in which I ran the MU tethers through the end doors and installed Kadees thru-out. Maybe the owner will take photos of the conversion and post.
I have not converted my Lionel SantaFE E6's or PA's, but did install Kadees between my Lionel F3's to shorten the gap.