This is the pinout for the Texas Instruments TPIC6C595. It can actually drive small inductive loads such as my 5v relays, but since i found the premade relay boards, they will only be driving an opto-isolator. I still have not decided on the design for the circuit layout for these driver boards. The red proto boards may not have enough pins for everything. I want the driver boards to be stackable, so  must ponder it further.