My house was built in the 60s and doesn't have normal plywood sheathing. It has that old sheet-rock-like sheathing (it's black, I think it is exterior gypsum). Basically the walls (right now) go, exterior gypsum > tar paper like stuff > foam board > vinyl siding.
I am not re-sheathing the house, so I am unsure if a house wrap is needed when re-siding. I'm hiring a company to do the siding and the owner said it wasn't necessary to install a house wrap, I was hoping to verify that with someone who knows siding.