We have heared a lot about different brands of suitable MT gearbox oil, as available in America.
Here is an alternative fully synthetic sort that might even be the most suitable of all. It is easily available outside the USA.
The brand is ROWE, the sort is called "Topgear FE S 75W-80 GL4/5"
Factory order number is 25066
According to factory, ( http://rowe-mineraloel.com/en/ ) it exceeds both GL4 and GL5, meaning it will not corrode or wreck the brass synchro rings as straight GL5 would, but includes better anti-foaming and anti-wear agents which exceed both GL4 and GL5 requirement, but without being harmfull to yellow metal. Data sheets can be downloaded from their pages, and you could also reach them by phone and ask for an engineer.
In direct comparison to Mitsubishi MZ 312644, it has the same neutral colour and same almost odourless smell, but is slightly thinner at room temperature, meaning it will shift better when cold. Being fully synthetic it has a less temperature-dependant viscosity curve. According to data sheets, it is also slightly thinner than Redline 75W-80 GL4
Below is a picture of a one-litre bottle, the same stuff I use in my Mirage/SpaceStar. See manufacturers compliance printed on the label.
I have also used it in other makers cars originally specifying 75W90 GL5 in order to make shifting easier in winter with worn gearboxes.