Nice find Mac. The older literature always listed the exhaust lift at .455". Then there are other specs like NHRA's that have all kinds of crazy numbers.
The new Purple shaft restoration "road runner" cam has slightly larger timing events on intake and exhaust duration at .050" than the original so it should build a bit more power.
New Purple Shaft "road runner" cam specs from MP:
Intake duration @ .050 = 228 degrees (208 degrees originally)
Exhaust duration @ .050 = 241 degrees (221 degrees originally)
Overlap = 46 degrees - same as original
Intake lift = .450" - same as original
Exhaust lift = .458" - same as original