.451 lift is not that far off from real good for a 318. You cannot just drop in solid lifters on a hydraulic cam They are diferent grinds (solid vs. hyd). If you change to a bigger cam, you will probably just make it a real dog off the line. I put a 270 with .490 lift in my old 318 and it was slower off the line and I had 4.30 gears. What are you trying to accomplish? ( street, strip or both). What car, trans and rear end ratio?