Unless the new cam has alot(more than a 068) lift, or unless alot of work has been done to the heads, you should still be fine with stock rockers and adjustments. After all that was the way they were originally made. Try chasing the thread with regular nut. The original rocker nuts are made to "lock" in place after tightened down. The stock 20lb adjustment doesn't require the lifter to be on the base circle. You might also think about getting some new rocker nuts becaue they are a bit like nylocs as far as after you run them down a couple of time they tend to lose that locking ability.
After all that said, an adjustable valvetrain is a better way to go. Worth thinking about if you have to replace parts anyway.