Smooth out a 360?

I have heard that all the casting bumps and small (non structural) ridges on a motor actually help in cooling, that makes perfect sence to me but if I were to smooth out the block and heads of a 40 over 360 how much difference in cooling would you think that would make on a daily driver? With a new raidiator and a 7 blade clutch fan I wouldn't think that it wouldn't even be enough to worry about.
I would be using a 80 grit flapper disk on a Mekita grinder to do the job. things like casting date and other numbers on the block would stay. This motor would be all shiney and metal flake, think 60's show custom.