you'll also probably need a new spindle pulley too as that one looks like it's a one piece with what would normally be the bull gear, plus it doesn't have the gear at the end of the spindle pulley to drive the back gear. You'll also need to buy or make a collar that stops the spindle pulley from moving back and forth on the spindle. The gears themselves go for around $100 or so a set too, unless you have a 3D printer to print them with.
They're nice little lathes, don't get me wrong (I have one), but if I had an SB9 and this I'd be selling the neutered 618 and putting that money into the SB9. I'm sure you'd be able to get your money back.