I know off the top of my head that factory 340 heads are pretty much done between .480 and .50
No idea what 273 is.
The zebra dart's 318 was a blast off the line. Had a pretty "mild" cam in it. Good for coming off slow and moderate turns. Only real issue was the car was going W2W road racing (summit point, VIR) so Dave needed to set it up more for high rpm. Point of that ramble is big cams are most fun above 3000 rpm, that's usually 65 mph up. Also useful in 1/4 mile.