'68 4-speed cam?
I went to the comp 268 a few months back. Wound up with a tap and posted here for help. Turns out the stock rockers were at the limit with a .480 lift. Switched to pro mag rockers. The comp 901 springs are not rated that much higher than the stock units, but remember the stock units have many, many cycles on them. They made a difference you could feel at higher RPM.