If you really really want to get in to it, I can dig up the info from the turbo guy at work. We mostly sell turbos for performance diesels, easier to change injectors and turn the pumps up...
With a gas engine it opens up a whole new can of worms. Depending on how much boost you want you will end up with a bigger fuel pump, injectors, have to get a custom tune before you even fire it up to keep from burning a hole in the pistons THAT IS IF you can use the existing pistons due to excessive compression ratio. Have never seen anyone do a dodge hemi but we have had a V6 mustang at our shop with a single and a killer camaro with dual turbos. I hate GM products and I would have been proud to drive this camaro it was down right wicked.
So what size? Depending on what you want to do with it. You can get over 700 HP with 10 lbs. of boost but it will probably cost you 12G before you are done. I dislike precision because they are a competitor of ours but they already have kits starting at 58MM inducer. It's a copy of a Garrett T04 IMO.