My '62 C10 has a 235 engine, and has a generator. Is it a 6-volt or 12-volt system? Reason I'm asking is that I put a new battery in the truck, and I got one with like 668 cold cranking amps, and it is a 12-volt battery. I just don't want to mess anything up and was wondering if I got the wrong battery.

Should be a 12 volt system. Was there an old battery in there? If there was and it had 3 cells then it is a 6 volt system. Seeing back in the day my 60 had a 12 volt system I am 100% positive yours does too.. Plus you can take your parking light bulb out and if it is an 1157 or 1156 that is a 12 volt bulb. Also I dought they ever made a 6 volt sealed beam headlight..

My 60 is a 12 volt. My nighbors 58 is also a 12 volt.If I am not mistaken 1954
was the last year for 6 volt
if you want to be sure,you can look on your generator ,or regulator it should be marked 12Volt .