thats a beefy drive cup. what is the intend diff box it goes into? losi?cutting it down, i don't know , may loss some toughness if cut... i think fitting the intended gear diff in the box would might be easier and gain tremendous drive toughness, even if you did the breakage point would be further up the drive line like pinions / center diff components. plus the degree of misfit would just destroy something else.
was the original problem dogbone length? is it on original chassis?
addressing these elements may keep it simple rather than a difficult mod.
if so, maybe redrill the outer A arms' pin shaft holes to bring in carrier close to diff ...a cheap plastic trial run first will tell u alot