The idle surge or roll that you refer to is mainly caused by the idle mixture or by using carbs that aren't boost referenced. The power valve is opening and closing due to the varying vacuum signal the carbs see on top of the blower making the mixture rich then lean. I can make the idle of the blown big block in my boat roll or be smooth by adjusting the idle mixture screws. It seems that alot of people like the "detroit roll" sound. I don't personally, but to each his own. The cam I am running in my boat would be a good street cam also. It has 224 deg. of int. duration and 234 deg of exhaust dur. with 114 deg. of lobe sep. The lift is .545 int. and .560 ex.
By the way, I am running a B&M 420 series blower.
I hope this helps.