You are thinking about the compact reactor 40 correct?
Read the fine print on the compact, I don't think it's the right autopilot for Tolmans/ Great Alaskans
¹Not recommended for fishing or applications that require holding heading while trolling at low speeds or operating in rough waters. For applications that require precise heading control, our higher-performance Reactor 40 models are recommended. Compact Reactor uses a gear pump design with limited performance relative to similar flow piston pumps. Not recommended for power assist installs, engines above 150 horsepower, or boats with more than 12 degree deadrise. Mount pump within 6 feet of the steering cylinder for best results.
²Requires echoMAP™ CHIRP 5x/7x/9x chartplotter/sonar combos; ECHOMAP Plus 6x/7x/9x chartplotter/sonar combo; GPSMAP® chartplotter series 7200/7400/7600/8000/8200/8400/8500/8600; or GPSMAP chartplotter/sonar combo series 7x2/9x2/10x2/12x2
³Auto Guidance is for planning purposes only and does not replace safe navigation operations.
I ordered a Reactor 40 with GHC 20 (separate display) and a 1.2L Pump for my Tolman.
https://buy.garmin.com/en-US/US/p/599938#overviewhttps://buy.garmin.com/en-US/US/p/pn/010-00705-64I wanted the separate display since I only ordered a 7" main display and it's a lot easier to hit an actual button instead of a touch screen in rough seas. The 1.2L pump is sized right for a single seastar ram. I wasn't sold on the shadow drive though it's included with the Reactor 40 so we'll see how it works, I can see it being nice when there's junk in the water. Unfortunately my boat is still in progress and not in the water so I have no real world experience yet.
As far a gps antenna is concerned Garmin said I didn't need one for their GPS/ Auto pilot though it will help reception in narrow inlets and allow for faster updates. If you want the heading function to work with their Radar you need a 24XD antenna, it's a NMEA 2000 antenna so it will plug into your NMEA network and talk to the rest of your electronics in the network.
I ordered from BOE marine, they were awesome to deal with and answered all my questions I'd give them a call before ordering the compact. They had the auto pilot, pump gps antenna, and chart plotter in stock. My transducer and radar were back ordered, I order March 31st and my Radar shipped Tuesday, the rest is all ready at my house. They said to backorder parts from them because with the current demand they will never show in stock and will be sold before they arrive so you need to get in line.