My son and I both run the solid MP .557 cam and he uses 3.91's in his Dart where I use 4.30's in my 63. But I can fit a much taller tire under my 63 as I run a 29 x 11.5 Hoosier QTP and my son runs 26 x 9.5 QTP tires. I drive my 63 on the highway all the time turning 3000 rpm around 55 mph and about 3200 at 60 mph. My point is if you aren't using a tall enough tire I would not go with the 4.30's as the 4.10's or 3.91's will work good with the right size tire. And as was said the .509 likes alot of convertor. Ron