I put in a small remote controlled $75 marine radio and hid it in a heater box on my 41. No heat required in Texas. I got a Turnswitch radio installed in an empty 36 radio box but was very expensive at $600-700. The first radio board they installed was horrible. Almost impossible to tune in a station and when you turned the car off and on again it wouldn't remember the station. I complained and Turnswitch said that is how it works, it being a feature not a defect. I had to pay another $300 to get the latest version of the board when a better one became available. I'm not a happy camper with them installing an unworkable radio board and making me pay to install another one that works. It does hook up to the original 36 radio knobs.
With all the PITA with Turnswitch I didn't go that route on my 41.
https://flic.kr/p/2cGTh5d