btw, folks, i "topped off" my MT fluid with a few OUNCES of synchromesh fluid and it made a difference. i didn't have much of a problem but the occasional clatter going into 1st on a roll. now i've been experiencing a little faster mesh upshifting, and 1st gear has been quiet.
in other words, you may be able to get by with a blend instead of going whole hog. this may assuage some fears about gl4 vs gl5 and lubrication.
the rest of the fluid is OEM at this point.
jm2c and another data point,