Hi!
We have 400 BB that is built with a factory block with sutds, forged crank, H-profile rods and forged pistons with around 8:1 CR. The heads are ported Stealth heads and the cam is a roller with around 260 degrees at .050 and 112 degree LSA. It currently has got an old who knows what supercharger, slightly wsmaller than a 6-71, and is working semi decently, but we might have a chance to upgrade to a 8-71 BDS super charger for a nominal price. But is it too big for this combo, what benefits or drawbacks would it have?

If it's a good deal otherwise,run it. You'll probably have to slow down the drive ratio to get it at the boost you want.An 8-71 is pretty good sized for a 400,but should heat the air less than a smaller bower driven at higher speeds. Are pulleys available over there at a reasonable price?

Yes they are, and the blower comes with 10% over and 10% under. The current one has been driven almost 30% over at most, but I guess hte heat was a problem since it didn't respond performance vice.