Well, I can tell you from my experience of 20+ yrs of steering wheel collecting and driving, racing, restoring vintage sports cars, most of them were 911s. Due to the lower weight on the front end, a 350mm wheel will do it BUT a lot of folks that are looking for wheels contact me and ask for 370mm steering wheels. I always have 2-3 wheels in the car and on long tours that I do in my favourite 911, I change wheels from time to time. But, if we're speaking about ONE FITS ALL, I would do bigger than 350, my favourites in those sizes are either the Momo Rally 2000 (which is a semi-dish) suede 360mm wheel or a 370mm Prototipo or Abarth. Here's a nice little article about it.
https://www.patipatina.com/best-momo-steering-wheel-for-every-purpose/
And if you're interested in the Momo Prototipo history, you might wanna read this here as well!
https://www.patipatina.com/momo-prototipo-the-legend/