Ok,
You can thank me later, but I have been day dreaming of the same application, but electronically actuated - like the new Lexus RX330 with power rear hatch.
Check this site out:
http://www.autoloc.com/products.lasso
and hit the link for Heavy Duty Linear Actuators.
I would love to see someone take on this project and post the results. By the way, this is the same brand equipment used on Monster Garage on TLC for those who are fans...
Also check out
http://suv.truckmoxie.com/
anytime you are looking for special parts, etc.