Mas dimensions and options
From the official German tables of dimensions:
7,5x54 MAS land/groove 7,57/7,85 mm
.308 Win. land/groove 7,62/7,82 mm
Normal .308 bullets are perfectly satisfactory.
Ammo options:
PRVI,as already posted
FNM (Portuguese) if you can find it.
If you are desperate, or just like reforming, then 6.5x55 Swedish cases can be neck-expanded (anneal first) and formed in a MAS die, then trimmed to length.
Original vs. rechambered.
You may not be concerned about this aspect now, but one day you may want to sell it.
I cannot judge the US/Canadian market, but over here a rechambered milsurp has approx. zero value. Hang on long enough and ANY milsurp in ORIGINAL configuration is going to get more valuable. Plus competition rules here usually ban anything but the original caliber!
And finally, the major MAS plus-point:
It is the cheapest milsurp available with a rear peep-sight instead of open sights. The backsight has range notches, but it is not difficult to fiddle in a sliding wedge to override the notches and achieve an effectively continuous adjustment for a specific range. And right/left can be achieved, in small doses, by taking up any slack, gluing in a small washer with a smaller hole than the original, filling and reboring, or just plain bending! BTW, the orginal had alternative backsight leaves, to be fitted as required by the armorer, but even my French friends can't find any these days!
Patrick