Ok guys, the Comp 270's are the ones everyones having trouble with, not the 262's. I've got the 270's in my current motor and had "0" piston to valve clearance.I had to notch the pistons for these to work, but I'm very happy with the results. It has made over 300rwhp with mostly stock heads and an unported bullit intake. If you aren't looking for the most power you can get out of it the 262's or the VT's will be much more simple to install.
330 rwhp wouldn't be too much to expect with the right cams, a good set of heads, and the supporting hardware.

David