Beware of using the REA Best, Princeton Review and other tests to measure progress. These are not tested against the same population of test-takers as are the ETS offical practice tests. Measure ETS against ETS. The other tests are great for practicing the testing style and environment. You can take one of the REA Best tests, for example, at a library under timed conditions. Get a feel for the pacing. Don't use the score, though, to rate your performance. Hope this helps.
I took the GRE Subject Exam--Literature in English in December 2005. I've listed where I've found three version of ETS tests at....
http://quiz.agencyinfo.org/grelit/
I've heard there is a 1982 version available in old "ETS Practicing the GRE Subject Exam" but I have not come across the test myself.
Good luck.
Mike