Rebuild 5.7 or buy something else?
The real pricy stuff is the engine management. If going the Hotwire oem ECM route you will also need a good tuner like a diablo sport intune. Unless you take it to a shop and have it dyno tuned. Either way costs. It's best to have a tuner and have it dynoed.
Or there's the carb conversion. Equally pricy if you don't already have a carb lying around. You have to get a 700-1000 dollar intake plus carb and MSD OR FAST ignition controller and wiring harness.
Lots to consider either way. The best thing to do is search google or bing and determine what the pros and cons are to each method. Then think long and hard about which way is best for you.
I have a spiral notebook with varying detailed methods to build mine and my desires have changed over time. After 3 years I finally have it nailed down and have been buying parts as I can.
Good luck and happy researching.
CM