Funny you should mention the destroked 340 to 5.0 litres , i was thinking about doing that , having an engine i could rev the crap out of , might be the way to go , as all i have now is a block heads and intake , how hard would it be to get 400+hp out of that destroked 340 . I'm looking for something different that if driven with a light foot like highway driving will match the mpg of my 340 about 22 mpg and pull low 13 in the 1/4 mile . i drive the car 120 miles a day so mpg matters , also ;l still like to have a bit of hp for some track time