The only other numbers I've seen is a 11, I think on the front of the engine block on the passenger side. Maybe between the exhaust.
I think I need to clean some more around the engine.
There's a T which I am guessing is for Tonawanda???
Langdon has this on his site...but mine could be '55-'58 and I don't see all of these numbers, mine looks different, but that could be because of all the wires and such...this pic says '58-'62. I'll dig around some more tomorrow.
![](http://www.langdonsstovebolt.com/wp-content/uploads/2014/01/235_261_58_TO_62_CASTING_NUMBER_PIC.jpg)
I don't see anything but I didn't see anything until I took a wire brush to the engine to get the above I first posted.
I have a pneumatic die grinder I can use a wire brush on, maybe that will make short(er) work of it, if it can fit in between the stuff.