Update on this - the ISN can now be reset on these and I'm happy to report that I successfully swapped in an 8HP70 from an E70 50i. Many of the earlier comments were correct. The old transfer case does not fit as the 8HP70 output shaft is longer. The ATC700 from the X5M will physically fit the transmission but is too long for the driveshaft. The ATC450 from the 50i is slightly shorter and works with the factory driveshaft, barely, however it requires wiring changes. In fact, the entire transmission + transfer case assembly is longer than factory as the N63 must mount the transmission further forward. This means the crossmember must be modified and the front driveshaft doesn't fit either. The F25 X3 front driveshaft is the correct length and splines into the ATC450, but the bolt circle on the front u-joint is smaller than the E70 so a solution is needed for that. Another big issue is the bolt pattern for an N63 is different than an N62, so the transmission needs modification for it to fit. The N63 does bolt on and works with the N62 starter. Otherwise the transmission works fine with the exception of a couple fault codes that don't set a CEL. I'm working on resolving those now, one of the codes is for the door status that can be resolved by fitting the later FRM and JBBE.