For what it's worth: If you can find a blower -- even if it's for a SBC or SBF and the price is reasonable, go ahead and buy it. It's going to be much cheaper and easier to "modify" that blower than it would be to purchase the blower new.
For instance... buying a new manifold to convert the SBC blower might cost you about $200+/-, new pulleys about $150+/- each, and you're in business! Buying this unit from any of the manufacturers would run you about $4000 to $5000 (polished).
If the used blower is in good condition, I'd definitely reconsider it -- IMHO.