I had a Sig 290 which was rack & pinion. Is the 370 hydraulic? They do make a mechanical one to drive the steering.
Hydraulic is much easier to install. You cut into the lines, add Tees and add more oil. Than make up your connections.
I never had one before until I got this boat. I would go with Simrad's A.P. unit. Some of my friends have Simrad and its very responsive in corrections. In other words, if the wind, waves and current push you the AP reacts very quickly.
You do understand that you will need a NMEA2k network, A.P. control display and a electronic compass.