on that motor it shpould be all on by 3k.
basicly you want to leave the runners/length as factory. its an awsome factory set-up. especally if you still have the standard cams, also it will probably throw a leg out of bed if you get good power. (there built very light internaly to rev)
all changing the runners will do is loose torque at low revs and make it laggier becauseof this.