I run 35's with no lift on my 87 K5. The front I had to trim only 3/4" from the back of the front wheel well. It is not even noticable that I trimmed unless you look hard. I don't run it that hard, and have not had anything break (yet). Gas mileage went down, but meh....
I like the 35's, I like the way they look. The are on factory alloy rims (7" wide), on factory 10 bolts. I'll probably do a 1" zero rate in the future, but otherwise I like the way that it looks.
and 35's allowed me to climb an 18" block where 31's wouldn't, so I'm happy with the increased diameter.