Grade 8 should be fine, might as well use 12.9, it shouldn't cost too much more. Also, go for ZINC if you can. Most people I know of are running Tubeless.
Centerline say you can run tubless with beadlocks, although I run tubes! I run tubeless on all my non-beadlocked rims though. I reckon you could run tubeless if you add slime no worries?
