I do not know how easy or hard it is to use roller lifters in the block you are using. If at all possible go with a hydraulic roller cam.
1) Roller cams work with today's
oil. Flat tappet lifters need more ZDP than is put in modern
oil. It was removed to extend O2 Sensor life. All modern engines have roller cams or overhead cams. Roller cams are more reliable.
2) Roller lifters can easily roll up a much steeper ramp than a flat tappet lifter. You can get the valve open quicker, and you can keep it open longer because you can close it quicker. This increases flow substantially at the same duration.
.600 lift is nothing for a FE head. People are running small blocks with more lift.