There were 2 different MP 590 SB cams. At one time Racer Brown was their cam grinder. His 590 had 272 @ .050. I know, had one and had it measured. The grinder now is different and their 590 is 265 @ 050. I know this because I just purchased one last year to repalce the RB that I hurt. Jim

PS: They performed about the same in the car. RB ET'd about .08 better, Same MPH with either.