I believe that the only former Lockheed building still standing is Building 90, which was the super-secure engineering center for the Skunk Works. It's a four story building made like Ft. Knox, located about a half mile east of the airport. A company joke was that if Burbank were ever hit with a nuclear weapon, Building 90 would be the only thing left standing. About 10 years ago, they stripped it down to the bare structure (which was immense!) and recladded it as an office building.
The former site of the Glendale airport, which is where the P-38's were assembled, is less than a mile from my shop. It's now an industrial park mostly occupied by Disney Imagineering and Glenair, which is a big supplier of aerospace connectors and harnesses. The original airport terminal building is owned by Disney and is being nicely restored. It's completely surrounded by modern industrial buildings, though. The Disney building which has the electronics lab, where I work part time, is right on the old airport runway. One other Disney building is WWII vintage, and was originally a Pratt & Whitney mechanic's training center.
It was sad seeing the old Lockheed buildings being torn down, but the truth is that most of them were in terrible condition. They were put up fast & cheap in the '40's with minimal materials. Time moves on.