thats because the ones that got beat on either chained them down or went to a motor plate.
problem with the stock stuff is it is usually very expensive. unless you have the mounts and k-frame already or can get them really cheap then its not worth doing it that way for a non-numbers car in my opinion. figure the schumacker mounts are in the $150 range and the DC mod can probably be done even cheaper then that by most.
i stand corrected on the booster thing, factory heads and factory valvecovers you shouldn't have a problem.
yea your right. stock style heads and i have found moroso valve covers fit a BB A-body very well. they have an angle cut in them that cleard the master cyl perfectly.