600's are just over stock and are required when going FI or even higher.
If you went with a stroker kit you would need to go to 600's as well to adjust to the larger volume of displacement. as other have eloquently put it: More Air = More Fuel... stock injectors are in the 400-500 range.
As far as fuel pumps it is recommended to go to a 255lph or even DW300/330 for even better consistent flow to the injectors.
Also think of spark plugs too... More fuel needs more spark
