Find the casting number per the link below and tell us what you find.

http://www.1954advance-design.com/Web%20images/casting-code-photos/codes-ser-nums.html

1960 might have had a 235. Your date code L199 might indicate 1959 casting date. But it could be any replacement motor. Show us some more pictures.
Your valve cover have 4 fasteners?

I will move this post to the engine pages where you will get more insight if you dont get answer here.
HB


~ HB
1966 Chevrolet K-10 | Ghost: formerly Flappy Fenders | In the Stovebolt Gallery
1962 Chevrolet C10
1962 Suburban