Paul,
              Went to my shed to photograph the actuator that is definitely
    there according to young John, and cannot find anything that even looks
    like one.  However the name of the brand is Thompson linear.  If
    you google them it all comes up and you can get as confused as me.  John
    said that the one on the harvester is about $600.00, but that is a big
    capacity actuator.  Have a look as there is plenty to choose from.
    Neil.


    This will do it.

    http://www.solidcomponents.com/company/?SCCC=SCCIR18EN&Lang=44&VisualID=22370
    <http://www.solidcomponents.com/company/?SCCC=SCCIR18EN&Lang=44&VisualID=22370>

    Built in limit switch. 12 Volt DC. 5 inches of travel.

    Paul Lamar
    --

Here is another option that might work for you.  The electric seat
adjustment motors in most cars have a screw drive and a 12volt motor.
They already have some sort of limit mechanism, toggle switch and are
probably dirt cheap at the wrecking yard.
Randy