I was thinking about just general performance boosts. I was also thinking about a supercharger and all the stuff needed to make that work. A heads & gaskets kit and Weiand 142 supercharger 4 barrel intake pack on Summit and a Holley Terminator 4 barrel EFI throttlebody from the Holley site. All together, those parts would run ~$7500.
I would hold off on the aftermarket EFI for a few months. At SEMA Holley revealed a new EFI system they will launch in 2016 called the Sniper, uses the same software as the Terminator, but has a self contained ECU within the throttle body. List price is going to be sub- $1000! Thats what I'm waiting for, like you I plan to put the Weiand 142 on my truck in the future.
If you want something more immediate, without the monster that is Holley backing the product, a company called FiTech has almost the exact same as Holley will release. Except it is for sale now!
Here is the link to the FiTech site, seeing as you plan on boosting, here is the Power adder package.
http://fitechefi.com/default.asp.pg-GoEFIPowerAdder
Don't forget you will need to upgrade the fuel system as well, and consider those costs. Have you considered just finding a set of used vortec heads? Save you alot of money there.