Smoothflow pullies can be run down to a 2.7 without machining the snout. I don't know about any smaller though. I do know that there is not much room left between the snout and the pulley though.
2001 GTP Drag Car - XPZ, Tischler heads, Upsidedown M90 IC'd, e85, Gen V, 2.3 w/ 5%OD
2005 F350 6.0 - studded, deleted, tuned
2001 GTP - cam, headers, nitrous, stock trans - 11.83 @ 116 <$2k in mods - sold