a friend of mine has the 291 in a 454...sounds good and pulls good but it is in a truck and it is not a 1/4 mile vehicle.Personally, I do not like them as they fall noticeably short on the torque on the desktop dyno. Granted the desktop is not the holy evaluater but it is based on an algorythym that is as accurate as the info that you input.
I talked to comp tech, and even they admit that thumpers are simply "noise makers". My suggestion is to have comp custom grind on a 108 lobe center if you want the noise. I guess it is all based on what your application is- performance or show. I agree with Tech. If you have the compression and performance, chances are, you will likely have the sound.
I am also a member of speed talk and I will say that Joe Sherman highly endorses the thumper series, off the shelf grinds. Joe is to speed talk as Pat and Tech are to club hot rod.