N941WR's comment about EFIS systems is something to be aware of. This will determine which specific AP options you have available. With the new EFIS systems that are on the market, most vendors have pulled the autopilot controls into the EFIS instead of having a separate "brain box" to control the AP servos. This really only matters in the specifics of which AP you add to the plane. The major installation items (servo mounting brackets, wiring to servos, etc..) will be very similar between the integrated/non-integrated installation. All the AP vendors provide installation kits that include pre-built servo mounting brackets.
If you get the plane and decide to add an AP, I have a TruTrak DigiFlight II VSGV that I'm needing to sell. This includes the brain box, and two servos. I believe the VSGV requires a GPS data source to operate. I switched avionics choices during the build and went with Dynon Skyview and AP instead of this system. PM me if you're interested.
Some folks prefer to have the AP control head completely separate from their EFIS, for the purposes of redundancy. The TruTrak VSGV, for instance, will keep the wings level and the altitude held, and remain completely usable for navigation even in the event of a complete failure of the EFIS.
Kurt raises a good point about safety. A separate autopilot head can keep wings level when the screens go dark.
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While true, having the autopilot controlled by your EFIS has the advantage of the AP knowing which way is up and down, not to mention the ability to limit control reactions based on G loading, speeds etc.
For example, if you try to engage the AP while in an unusual attitude, if it is controlled by your EFIS, it may be able to right the plane and fly on. Some of the non-integrated AP's simply hold the current heading and airspeed, which may not be a good thing.
Get your popcorn out, this discussion can go on for hours!
Bill, what autopilot do you have in mind? Not the Trio Pro, which boots up to wings level and altitude hold mode, and contains g-limiting and airspeed (both too high and too low) limiting.