I will jump in here on the cost question,a few years ago I was building a pro-touring car, I priced out the build with a 6.1 Hemi 425hp or the LS3 hot cam with I think 420hp. By the time it was priced I think it was around $5000 more to put the Hemi in the car. The engine management system and aftermarket bell housing needed to adapt the transmission, TTI headers cost a lot more than the ones for the LS, the front accessory package was more, the motor mounts cost more ect.
This shop had also done both engines swaps in other cars a few months before I priced mine out so they had a good idea what it took to do either install.