That sounds like a good start. Just keep in mind, shipping on those batteries is from China, so add a few hundred dollars to that.
Bogan, He's probably ordering some extra. 120cells would be 24s5p on the 16Ah batteries and be 80Ah. Gonna be hard to fit, but ordering 5 extra sounds like a safe plan. I ordered 20 extra.
Some missing things (sorry if I repeat Bogan):
Contactor, depending on what controller you use, get an EV200 from ebay for ~$70
DC-DC converter to convert back voltage to 12V so you can run lights and BMS if your BMS runs with 12V
Front sprockets (surpluscenter.com has them for under $5, use #50 sprockets, it's the same size as 530 chain)
Rear sprocket (sprocketspecialists.com, get it for your bike and get 530 chain size, it'l be easier later.... finding front sprockets in other sizes is a pain)
Chain, it'l be longer than original, surpluscenter has this too. Get a chain brake too.
Gauges of some sort, consider a Cycle Analyst.
Fuses, welding cable, emergency stop (or you can use the engine kill switch)
BMS, might as well use a miniBMS, it's good bang for the buck. Just wire it to protect your batteries and you're good to go.
That should be good for now.
Let me know when you want to pull the trigger on that charger, won't have them for long.