273 adjustable rocker arms

That's correct.
If the new springs have a larger OD than the stock pieces, and/or you're using aftermarket retainers, you will run into the rockers.
As you can see with toolmanmike's great photo, the stock retainers provide lots of clearance, but the Comp retainers (and others) run all of the way out to the edge of the spring. and they will hit.