I have a 1980 C-10. What model should it look like?

According to any catalog I've seen it looks like an 81. Is there a way to figure out what number it was in production? The truck has under 50k miles and is original with exception to tires brakes and nearly all rubber hoses. It has a 250 I-6 and 3spd w/overdrive. How crazy would it be to place a V-8 and auto in it?