1.5 or 1.6 rockers on magnum heads

Magnum heads came stock with 1.6's but 1.5's should work. I would mock up the heads/valvetrain on the block before bolting them down and make sure the pushrods have enough clearance with the 1.5's.

Nothing wrong with a lot of lift other than valve guide/retainer clearance and spring bind issues. Of course if your heads won't flow past .500 lift it's a waste of motion but it won't hurt anything or reduce driveability.