Hi Zane, make sure the engine number starts with a 2 also, so it is a genuine 75.Engine number starting with 1 is OK also. If the engine number starts with a 3 or more,or has no engine number like the one I got dudded with, it could be 76 or later and not as valuable. There are a lot of parts that interchange but the head /barrel of the 74/75 wont work on the 76 and later - but they fit. The later model lower ends fit the frame also so beware!
There are plenty of parts still around for them and they are the best bike in pre-75 125's. Good examples are getting around $4000.