joeskin:
Auger-cast piles can be installed in low overhead conditions. I would suggest that you talk directly to auger-cast pile installers such as Berkel & Company for size and height restrictions. Another option that can be installed in low overhead applications are mini-piles. There are several geotechnical specialty contractors that can give you ideas such as Nicholson Construction or Hayward Baker. They can both be found on the internet.
Glen