Hello, Dan,
You might as well first determine all you can about what you have: your 235.
Find and post all the codes shown here.I assume you have checked out the GM/Chevrolet Specifications Manual for 1961, to see what engine was standard equipment, and what were the options?
I'll check it out, but,
here it is - enjoy searching through it. As I dimly recall, the optional engines in that year might not be clear. I'll post what I find.
261 and 283 were standard engines, depending on the 60 series model. The S67 model had a 348 Workmaster special 8-cyl engine.