yes the reason why 4.7 s are weaker is size of pinion, 4.7 pinion is a fair bit smaller which is also the reason why you need to add a machined spacer between crown wheel and 3.54 diff carrier if you wanjt to fit 4.7 crown wheel, pinions will fit whatever ratio in to housing, though if you use later 4.7 diff carrier that uses rtc2726 carier bearings ,the 4.7 diff carrier etc will fit the 3.54 diff housing