Just thinking out loud . How big of a blower would I need to make 300 more horsepower on my smallblock ?
71 series or a centrifugal?
That would really depend on the rules of the association you are racing with and your personal taste.
There are nostalgic organizations that do not allow centrifugal blowers. They require a roots type blower. On top of that some require it to be a standard roots blower and do not allow high helix rotors. The NHRA Nostalgic rules stated that the first year, and than amended their rules to allow high helix rotors.
I don't think a centrifugal blower would look very good on a FED