How about a Corvette engine in my Hummer?
 

GM will introduce a 2014 Corvette Stingray with a 450 hp engine that can unload to run on 4 cylinders for better mpg.

http://www.freerepublic.com/focus/f-news/2998927/posts

Can I get this engine installed in my 2003 Hummer H2?

Re: How about a Corvette engine in my Hummer?
 

It would never go into 4 cycl mode, even the tahoe and such rarely go into 4 cycl mode. So the added mpg is lost.

And for the price to buy a brand new LT, an engine that's not even in crate right now, well idk if it's possible would probably have to buy a new corvette just to get an engine.

Then everything has to be rewired since it's an entirely new generation of engine Tons of parts have to be fabbed.

If I had to put a conservative price on doing the swap at this moment in time 3/20/2013

I'd put it north of $70,000, that's a LOT of fuel

Your not going to get fuel efficient you can however change fuel type CNG for example.
And if you want power your much better off tuning your engine possible supercharging and then swapping in a 4l80e for that power