What year is your truck?

[old cool]

Seriously. Ok, not talkin about title, vin, or body components. I'm speaking about trucks that have non orig motors, frames, etc. Everytime I step up to parts counter, the first question is, "What year is your truck?" So, I go through my usual comment, "The parts I need could be any number of years between early sixties to late seventies. You who have non matchers know what I'm taking about. You could have a casting date that ends in a "5" and that could mean 1965 or 75. You could put a 65 valve cover and air cleaner on a 75 engine and you might be stumped if you don't know your motors.

SO, here is my broad question regarding this dilemma: I know I can pull the valve cover and find a casting #. I know the basic engine components are probably the same; perhaps pistons are different. And I understand I can walk up to the counter and match parts. My predicament is that forums are separated from 60-66 and then 67-72 and so on. Are the forums separated because of body and interior parts, or are the smalls (like ball joints, harnesses, grommets, etc) different. I'm sure there's an obvious answer but I would greatly appreciate an explanation that makes this journey a little easier. (Presently, I need front end parts)