alright smithkid, this is my:let me start off by saying i admire your ambition, (OK here it goes) if you can get a free cummins powered truck than get it! no brainer, drive the wheels off it (or transmission out of it whatever comes first). would be a cool swap into the(i cant let this one go)- ''worth 9k suburban''. ok so now you probably don't like me that's ok- i'm not done yet. I had a 2001 sub with 8.1 4x4 loaded, it did have a 6'' lift and 35's mpg: 11/12 thats it. it pulled great, and you might get close on your target mpg's on stock suspension. however i don't condone the swap. the guys that have suggested 6.0's are right. and last but not least you said there are ''NO PARTS'' and i quote again: ''NO PARTS''(all caps)for a 454? are you kidding??? The only thing you are limited by is the sky and your wallet on building the 454 that is in your truck. if someone gives you a complete donor truck to swap from then have at it! and post the progress or regress or whatever. if you must swap then 6.0 or, better yet the cummins- sick! you would have your power, fuel mileage, and more important than anything else, the cool factor. sorry i had to be like this