My boat originally had a Raytheon 1000 Autohelm [Raymarine] and I replaced it with a Simrad.
The old Raytheon tiller bracket was re-used and also the cylindrical socket attached to the mounting block screwed to the hull. As far as I remember, the old ball was also re-used [if not, it was easy to swap. The other thing I had to do was move the anchorage point attached to the deck by a couple of inches or so because the Raymarine and the Simrad were different lengths.
No problem, I interchange a Raymarine 2000 and a Simrad TP30 regularly, I think that the lengths of the two units are slightly different, but in practice this causes no problem. Even the plugs on the two units are the same for the 12v. connections