Why not a 5.3 LS4 setup from an '05 - '08 Pontiac Grand Prix GPX? Around 20 average MPG, 303 HP stock and over 500 HP available if you want to add a turbo later. The 3800 can't compare can it? Or does the $3K budget requirement overrule?Tony Paul put one of these in his Diablo and is happy with it. I am considering it myself.
Hold on I would first check the condition of chassis then suspnsion/ steering stuff brakes etcThen get the engine / tranny of yor choice etc. this is not a couple months project even if is half build if you rush it will not look likw a clone and people will laughing at it and you going to get the car stolen and collect from insurance. But you could be charged woth fraudSo take it easy and think twice before you do anything