water pump and pulley selection

This is for a moderately built small block on the street. My biggest concern is never having this thing overheat.

Water pump selection - there are a raft of aftermarket water pumps for small blocks out there and 6 and 8 impeller stock style pumps. What is the best choice for making sure my small block Dart never overheats even if I get stuck in a traffic jam in Palm Springs in August?

Pulley selection - to complicate matters, when looking through my bin of used pulleys, the AC water pump pulleys are smaller which I think means they spin the water pump faster If I can figure out alignment, should I use a smaller pulley?