Unforunately the M-305 isn't available in the states. Odds are it won't be either. Too bad too, as it would make for a low-cost alternative.
Some M-14s' have soft parts and the headspace "grows" pretty fast. It results is some having excessive headspace rather quickly. Others last forever. It's all luck it seems, as there's no rhyme or reason to the condition, other than poor quality control on parts.
The reason to have it checked by someone who knows military rifles is that the M-14s is a military chamber, and on miiltary chambers the headspace is looser than on civillian chambers. So a civillian headspace guage you use on a Rem 700 for example may give you a bad headspace reading, when the headspace is actually still good in a military gun. This mis-diagnosis may be the cause of many of the poor headspace ledgends on the Chinese guns. Much of it they have earned though.
You can get headspace gauges yourself, and they are easy to use, if you can find no one. Just make sure you're checking with the right gauge. There are many field expedient ways people will tell you to use. I personally don't like them for a variety of reasons. They simply aren't accurate, and with headspace I like to be accurate. Gauges are cheap enough and not much more than it would cost you to find a smith, get there, and pay him to check it.
Ross