does anyone know of a fly by wire throttle retrofit system for a typical efi big block set up ?

They're sold for big cruisers generally. Check out a Power and Motoryacht, you'll see an ad in there.
Gary

where do i find " power and motoryacht ? " is that a mag or a web site ?

Magazine, on the news stand.
Not sure if they have a website.

It would be cool to have a trigger throttle on the wheel sorta like a hot foot.

They're getting to be standard on water ski boats. Could try Pleasurecraft, Indmar or Discount Inboard Marine(Skidim.com) My Ski Nautique has this.