8' should be fine, but remember- that would be FINISHED height. Before roughing it in, consider everything that will be going above the work area: lighting, electrical supply, HVAC ductwork, exhaust/vacuum ducting, etc. to determine what your rough-in vs. finished ceiling height will be.
Span will determine what size your floor/ceiling joists will need to be, which in turn may dictate the direction of your installed joists in order to maximize and simplify the installation of any overhead utilities- I would guess it to be 9' minimum, 10' preferable in order to keep your finished ceiling at 8' or so.
