5.9 & a solid roller

I´m also interested in a solid roller cam, do have a pre-magnum LA-Block factory equipped with hydraulic roller lifters. As far as i understand, some solid roller lifters can be used without any block mods - it would be great if you can tell the part no´s and manufacturerers of these....and why these are ok to use. I always read about block mods with solid rollers....but really do not know the cause. Thanks!

Michael