I believe all F.I. have their perks and flaws, if I was you I would keep the centri and maybe put a larger serp belt or a cog and live happy...nothing beats the sound of a centri...
I had a 2v GT with a roots blower on it with a stalled auto. The car was a blast around town , the instant torque was great for passing in traffic.
I just recently just bought a 97 Cobra with a Novi 2000 with a 3.4 inch pulley. I haven't got to drive it much with the weather but it kind of sneaks up on you quick when the tach swings up you better be holding on.
The way I look at it if I was going to do a Roots type blower it would have to be an auto for a stick shift car I;ll take the Novi for now.