all it is is a 16 bit shift register, so I dont see why it would be that hard to just emulate a shift register with the 18f4550, but I'd honestly go for something cheaper rather than wasting a chip that has built in usb on an application that doesnt use usb.

also, you'd need to limit the voltages to the PIC chip due to the old chip running on 7v and pic chip only taking 5v max.