You can use an N62TU but you will need to drill new holes for the exhaust manifold. Would be a lot easier (and likely cheaper) to source. 4.8is and 4.4i transmission is not the same, for starters, the torque converter is a different unit. Not sure what else on the transmission is different. If its just the TC that would be great. If not, get ready to source a 4.8is transmission. Would love to do this swap too, but for now my car is relatively low mile. 4.8 swap in a 4.4 should be faster too, thanks to the 4.10 diffs in the 4.4. At least that's what id assume. Good luck.