Thanks, Ripley. Those were 2 of the photos I relied on (the second photo is a modified and painted version of the resin kit shown in the first photo). The M3A3's interior was different to the M5A1's, but I decided the approach would be the same. There are very few photos of M5A1 Recces, as the M5A1 was only issued to a few British units, but I've found 3.
I realised that Rubicon's Recce 'turret' is not completely circular. I don't know if this was deliberate. It's won't be very obvious once the machine guns are in place.