Just picked up 250 blowers. Premo condition B+M's They came with Nickerson carbs with NP 287 stamped on the top. My question is the carb has an AN fitting in the front metering block and the intake manifold has one in the runner and a regular fitting in another runner, most likley a boost gauge fitting. Are the AN fittings connected togeather with a hose? What is boost refrenceing a carb? This setup has teeth on the pullys not radial grooves. Which is better?

radial grooves are coast guard legal and cog style blower belts are not. most of the time you wont have an issue but you never know.
as for the fittings i would say they are for boost referenceing. i could be wrong, but i dont think so.