I'd get the PCM, the sensor harness, the front accessory drive, maybe even the transmission and TCM to start.
Considering what vehicles he would be able to get a 6.1 from (Charger, Challenger, Magnum, 300, Grand Cherokee), all of that is going to be useless. CANbus PCM, NAG1 (WA580) transmission, LX or WK harness, backwards ass front accessory drive (opposite rotation and different location accessories) and an LX/WK TCM that he wouldn't be able to use.
Hence the reason I asked what I asked, we don't know if he's doing this himself, what he has access to or is capable of, what he can afford, etc. There's a cheaper way to do this successfully and then there's more that can be done that is more complicated and correspondingly more expensive.