I fitted an xt base on my 2019 RT, the two bases use the same holes. The power supply shouldn't be an issue, just crimp into the cable. It was a little more complicated on my RT as the Nav fits in the cowling. There is a company the makes a 3d printed job that just clips onto the existing Nav mount, taking power from that and you then fit the xt mount to it, so the mount is removable as is the original Nav. Now not sure if that would work in your case as it was designed for the later RTs. But it might be work investigating. There was a thread on here about mounting an XT to an RT, so do a search. I just removed the bolts from the original mount and mounted the xt mount with spacers forward of the original mount, leaving it in place. I used the same power take off that the original mount used