I'd like to think photos exist, but I have yet to find any and I've talked to about every (if not all of the) DST employees still alive from that era, and some that have passed on. Quite a few attended the Thunderbolt Reunion dinner we held last Friday.
BTW, the building on Trowbridge was only used to build the first eleven burgandy cars. Hollowell Engineering on Bailey St. was the location used to build the white cars.
Perhaps, someone may of snapped a photo as a visitor or driving by. However, most people in the early and mid 60's simply didn't take photos like we do today, especially at work. The fact they did work on prototypes, cameras were most likely not allowed on site.