11:1
A friend of my brother's was all about compression, actually built an engine that had 13:1 on "paper." He was disappointed when he tried to run it on pump gas.

Be reasonable with what you do. You can easily have 2 grand in putting a stock 5.0L into your truck. It's not so bad compared to other things, but there are other costs. If you don't have much money to work with, right now I would recommend setting a goal of just getting a stock engine in and running. Once you're happy with it and know where you stand, then start modding the engine so that it functions as you want it to. There are other factors like rear suspension, rear end, etc that will all need upgraded to handle that kind of power.
Actually get an engine, trans, do some reading in the tech library and start gather parts for the swap. Once you think you have all of it and have at it, I guarentee you that there will be more to buy.
Pete