The 280/.474 acts more docile than the 284/.484, it's around 10-12* smaller at .050 than the 284/.484 from what I was told, the 280/.480 crane has similar manners to the 280/.474 if you have problems getting the MP cam.

I used to get 11-12" of vac at idle in gear with that cam where one of my friends was running the 284/484 in a similar 360 and was getting 8-9".