thanks for the reply. I found a couple more. Im going to call on them in the am and see. It does look like most are as you describe.
Im going to use this for steering so not sure timing the motor movement will be good enough to reliably center the shaft when there are other forces applied to the wheels. It ranges from x seconds per inch at no load and half that at full load. Thats why im looking for position feedback.
cheaper
http://www.ebay.com/itm/NEW-XSCORPION-6-Linear-Actuator-12-Volt-DC-450-LB-Static-w-Adjustable-Stroke-/350585835964?pt=LH_DefaultDomain_0&hash=item51a08b51bc
Potentiometer: 10K
i like these guys I just got a servo from them and the customer service was really good:
http://www.servocity.com/html/115_lbs__thrust__linear_actuat.html
Built in potentiometer can be easily accessed for position feedback but is not necessary for operation.