What voltage are you going to run it at? for 20 LED's in series you'll need a pretty high voltage (if the leds have a 1v voltage drop, then they will have to be connected to 20V)
You will need to use a transistor as well, These logic IC's typically arent designed to handle high currents. Also, you can have 2 or 3 (or more) transistors connected to the latch, so you could run 2 sets of 10 led's.
Any general purpose transistor should work, like the 2n3904 or 2n3906.
Which one of the 2 to use depends on if you want the leds to turn on when the latch is low or high, you'll want a PNP for low and NPN for high.
Hope this makes sense, I gotta study for a diff eq :roll: test now so I cant get into more detail...