The Megasquirt system is dang near as universal as you can get. There has been so much development on it over the years that you can make it work with just about anything if you're patient enough. It's probably pretty close to the cheapest injection setup you can get, and really not necessarily that difficult (in my opinion at least), but it very like takes the most patience of any of them out there. A ground up MS build isn't exactly plug and play, but you can start easy and gradually work your way up too. For instance, I started with basic O2 feedback and IAC control and have gradually worked up to PID O2 feedback and still working on closed loop IAC on and off. One of these days I hope to get some rudimentary knock control if I can figure out the sensors.
However, there is a plug and play Hemi MS system now. The Megasquirt Gold has a Hemi configuration that comes with a harness and is preprogrammed to work with all the stock sensors I believe. Granted your tuning might have to change depending on your particular engine build, but it looks like a pretty slick unit. I believe the going price for the whole system was around $1200 last I saw it.