Not sure what your definition of remote is so hard to say what you are looking for.

4x4 OHV places include
Barnewell
http://www.barnwellmountainra.com/

Red River - Though no street legal trucks on trails so this may not fit your list)
http://www.redriveratv.com/index.shtml

Hidden Falls (Marble Falls area)
http://www.hiddenfallsadventurepark.com/

Brazos Valley Off Road Park
http://www.brazosvalleyoffroadranch.com/

Try Rider Planet to see if a more comprehensive list comes up.