I have a 270 and it performs great in normal driving. Pulling a trailer it doesn't have the grunt I want, but that is probably my 3.08 gears as much as anything.
I don't think the big GMC motors are as hard to find as you might think. I've had a couple come and go, and have found others without looking.
Just let people know you're interested, and if you're a little patient you'll have one.
