My old humps on my 283 were not doing to well with the original setup, they had a big solid cam and still had points. I had a set of completely worked 305 heads so i put them on along with a 480 hyd cam, electronic ign steert dom intake and a new 650 edlbrock. It runs better than I expected around 7,000 rpm's.
On the other hand a knew a guy that had 305 heads on his old 350 nova and all he good get was 5000 rpm, when he put the cammel humps on it gave it much more power and 6000 rpm's.