do NOT use DOT 5.0. I've seen issues that I call "caliper worms" when the fluids mix and I've heard good arguments that our seals are not meant for it.
Yes, someone will chime in that they put it in their pickemup truck and they get a better pedal. They now use it in all their cars and they've had no problems and we're all insane but, as the Cap'n suggests, DO NOT mix the fluids.
These worms are hardened fluid that gels in the lines when mixed and, through the force of the master cylinder, this "paste" gets pushed into the caliper bores. 914 rear calipers have very intricate mechanisms inside the pistons and these caliper worms can gum up the mix.
Use 4.0 or 5.1 fluids. ATE or Castrol are some of the best.