I have some <nobr>cheap</nobr> r/c tanks that the control board went out so I am thinking of installing servos and a real radio, problem is I need a mechanical control device. Would have to turn on both tread motors, back and forth and individual side back and forth. Any such animal exist.

John,
Welcome to the forum.
The short answer is this http://www.dimensionengineering.com/...abertooth2x5rcas long as you don't care about sound or battling your tank and just want to drive it around. If you want sound effects there are several other options, such as using newer Heng Long electronics or Tamiya Electronics or using several other companies electronic systems. Check out some of the posts on the forum here and you will find many discussions regarding upgrading the toy gradeelectronics up to hobby grade. Youprobably won't have to install servos as many of the systems can use the hardware already in the tanks.
Steve