...they can be made to run well, but the money you'd sink into them could arguably be more easily invested in a set of Magnums for a bolt on increase in power and torque...
Mopar Muscle did a build on the heels of the Hot Rod build and they used KB pistons, a COMP 280H Magnum cam, and a set of untouched Magnum heads...it squeaked out over 400. IMO, they did have a better setup from the get go.
I'm kinda surprised it made power as high as it did with those heads, but if I were looking for a cruisin' engine-that would be a fantastic candidate for my '72 Scamp. And I'll vote my support for Tim's assessment that it would likely surprise most in a [pre-smog] A body.