Here is where I was coming from. In my Coronet Convertible I built a stroked 440, I think around $7K for the engine, added an expensive EFI around $4K, but even a cheap TBI EFI is over $2K, added the expensive Billet Specialities belt system (that comes with all new water pump/housing, A/C, alternator and P/S pump) so add another $4K, the on OD Transmission $4K for a total around $19K, even on the cheap the same stuff will be over $10K.
For my Coronet Hartop project I bought a 50,000 mile 2008 6.1L Hemi with NAG transmission with computer and all the accessories for $4K (OK, I got a good deal here, but 5.7's are much cheaper). If I use the Schumacher engine mounts and oil pan that will add about $650. The Electronic shifter about $100, and electronic gas pedal another $100. The trick part is wiring and re-programming the computers, but the high end of this would be around $4K, and I'm looking at less than $3K right now. I will have to modify the trans tunnel and fab a crossmember, and I could even make my own engine mounts and oil pan if I needed to, but for costs, I'll just use stuff you can buy.
I'll need a driveshaft, but thats about a wash with any of the drivetrain swaps. So for me the swap will be around $9-10K, for the engine/trans part of the drivetrain. The stock 6.1 is 425 HP, and 500 HP should be an easy cam swap and reflash of the computer.