I have a 38 Catalina docked next to me at the marina. See the name on the boat in the photo. They were all fiberglass. I believe it has the same general hull as a Commander, and I believe some of those Cat hulls are identical to certain Commander hulls. My 38 Express is a 13' beam, and that next door Cat is wider, so it's not an identical copy on that particular model.
They made some really find Catalina models too, including that sweet 28' Sportsman with the twin 307Q motors. The 33' Sedan/Coho Sedan (273 made) is also a nice model available with single or twin gas, or tsin Perkins HT-6 diesels, featuring a very large flybridge which is actually an upper deck on this model because it's so big.
I think the Catalina line was offered as a lower price point than the Commander line, but in later years they made Catalinas up to 48' in length, and any of these boats could have been badged Commanders, as far as we know, because they were big, strong, well appointed, and had plenty of power options too. Why they chose the Catalina name is a puzzle to me. Most of the Cats are good looking boats, but there are a few that are pretty strange like that 31' Catalina of 1971-72, of which there were 60 lucky and eccentric owners
Regards,
Paul