Hello,
i have to make a you a question, if you tend to mux 50 bytes per second, like Year said, you probably not be able to view characters with an useful brightness. I should make this thing ,instead:
Make an static driver for one character map, i mean 5 bytes, so i recomend you to use a shit register with latched buffered outputs to drive a single led. The common annode or cathode of this character map will be pass trouwgh a power transistor. Ok! this register will come with CLK, STROBE and BLANK signal. Then BLANK signal is to make brightness control. There are IC in MICREL, MAXIM, with this characteristics, i think they were TPIC or MPIC.
Well once you have this done, you have to join all single Character leds to this outputs. then you will have 10 transistors. So you will have three control signals to control bytes and then control signals to decide what character to display. to make this more easy you can use a shift register for these 10 signals so you only need now two sgnals CLK1 and STROBE1. and that's all, now you mux time are reduced to 1/10 instead 1/50.
regards