Lotta folks like these 660's.
To be honest, I'm not really sure why. I've played around with them a bunch, and sure, for a race car they seem like they'd do just fine.
For a car that sees the street, well, they lack a power valve. So in order to run right, they need to be jetted for WOT. This makes anything else involving the mains not work well.
I mean, I can water my garden with a fire hose, but it sure makes more sense to use something that works a little better for the intended purpose.