I have a 350 and I see roots blowers going for about $800 on ebay. They are the 142cid blowers from b&m. I've been thinking about getting one.

 

thats a decent price for one in good shape, plan on cutting a hole in your hood!

 

I am almost ready to start putting together my 8-71 blown 355. I am stationed in italy and I am still waiting on a few parts. Small stuff like main and head studs. It has taken like a year to get everything over here.
I sat the AFR 210 heads, intake, blower, kuhl superchargers inline carb intake, carbs, and scoop on the block. Just to see what it was going to look like when it is assybled. Looked hard core. Can't wait till the engine is finished. from the intake to the top of the scoop was between 22 and 23 inches so mabey it isn't for everyone.
Good luck on what ever blower you decide on.