I saw a 427 with fuel injection on ebay here:
I'm not sure if the 427 parts are interchangeable with 428 parts or not, but at least you know you can go bigger than 390.
Just found Kinsler Automotive, http://www.kinsler.com/
, they have injection systems for big block for V8s with aluminum heads. You may try them. 248-362-1145.