Cory and Paul: Thank you. As I said, they both came WITH roofwalks, so that isn't an issue. I removed the walks, plugged the holes with Evergreen 0.08 styrene rod, and filed the plugs to shape.
And the BREX car, at least, is more than 15 years old. We've been in our current dwelling 17 years, and it moved from our former house. As far as I know the WFEX car was purchased here, but I can't swear to that.