Most will NOT be able to do a 3.4 and only limited support mods without knock. I was only able to run a 3.4 after headers, 1.9 rockers, 180*, Wizaired. Still had to run rich to pull it off though. I would have been faster with a 3.5 and leaner AFR. However, I've always had a scanner/tuner and have kept an eye on things through all of my different stages.