I'm not in disagreement with Charles on this, but i did a similar swap about 9 yrs. ago in a 406", from a .595 lift flat tappet cam to a .625 roller 106 lobe ctrs. spent close to $1,000.00 and only gained 1/10, but i have to admit i've never in my life time of racing seen a better flat tappet cam than the .595 bullit cam which i still own. My friend Jimmy Smith can verify this because he knows when i did it. There's no question in my mind that the roller should run better, it just did not do that in my combination @ 3250 lbs.
Zip.