Except it won't work properly, Won't have the right stuff needed, will do have to do double the work.
If you wanna be the one to suggest he does double the work and finds things out the hard way, have at it. I've already been there, learned the hard way. It was painful.
He can get an engine relatively cheap. Swap all his accessories (ps pump/ac/alternator) to the new engine. Drop it in add a $20 wiring harness that he gets with his $100 reprogrammed pcm (Intense is my suggestion, they have the info/history to do this easily) then it will work.
On the trans, why pull out a good trans? The differences from regular to HD are pretty small. If he does the HD upgrade, that would give him 3.29 gearing and he'* have the SC motor and most desired gear ratio. I can buy HD upgrades at my JY for $50-$100. I'd suggest that anyone looking to do a swap like this does a lot of research and learns all the various options/cost saving ways before jumping in. I'm all about saving money because I'm a cheap guy, and saving money means more for mods later.