I have a 40ft sailboat that does 8-10 knots and would like to install an Autopilot, what drive do I use?

You can use a Hydraulic Linear Drive made by Octopus (Part #: OCTAF1212LAR12 or OCTAF1212LAM12). The LAR is a remote mounted pump and the LAM has the pump mounted on the cylinder. The Autopilot Electronics will have to be purchased separately through a Marine Electronics Distributor.