By the time it appeared in the Presley movie, Bill Mitchell had added the passenger seat and passenger side windscreen with outside mirror set-up.
When it was originally raced, it had a red interior and driver side headrest. There was no passenger seat or passenger side windscreen, just a tonneau cover over that area. Although the pic of the No. 11 racer shows it without the tonneau cover, isn't clear to me if it has the passenger seat in place but I'm guessing not, just in the interest of weight saving.
As he funded it (I'm sure never worked on it while on the clock!), it became Bill Mitchell's personal car after the race days were over circa 1960. Changed to black interior with two seats when seen in the movie but still red exterior. Also the hood scoop was added (maybe just for the movie) and then apparently removed at some point. The functional hood vents were also shorter when originally raced, became longer at some point.
Not sure when it was changed to the silver exterior with silver interior as it now appears for the Tech Center iteration. It remains in the two seat configuration rather than the original "as raced" version.
The race effort was privately funded by Mitchell because of the GM racing ban in effect at the time.
Is it my imagination, or is the side pipe disconnected at the fender in the shot with Presley standing against the passenger side?
Footage of it racing at Elkhart Lake's Road America circa 1959 or 1960. It can be seen starting at the 2:33 mark.
https://www.youtube.com/watch?v=OsaP_LzUl3Q