Jason, the guy who started this forum, IIRC broke the M46 he put in his 760 on the very first day. Forget what kind of power his motor was putting out but it was significant, enough to break pretty much everything behind it, he blew up a rearend too later on at some point - though he did have a major six puck clutch of some kind in it, which no doubt was part of the issue.
Nevertheless, worth noting that the ~200k mile ZF autobox he had in there before the M46 held up under the same kind of output for months or years...
Anders, you're running studs as well, no? The first weak point on these in general, increased power or not, is headgasket and engine cooling. I've never tried turning one up the way the big HP experts on here have, but my uneducated sense is that provided you're careful with timing, engine temps and EGT, and ensure it's breathing well both on the inlet and outlet sides, the margin is quite big and you can safely push it quite far. Studs and a fresh headgasket might be a good insurance policy, but if you're careful and you aren't romping on it all the time, you probably can do a lot even with the stock stuff.