You need to do a compressoin test to figure out your octain (with 17cc domes your probably gonna need 110). Also do you have a timing plate on it if so what is it set at? Do the test and let us know what your psi is. As far as oil I run 927 40:1 with 110 oct, but what oil you run is your choice there is alot of good oil out there.
Trinity will send you some just give them a call monday. I ordered some a few months ago i think they were $15 or $20 a set, you may want to order a couple sets just to have some extra's.
After you take the nuts off it should slide off. If the pb blaster don't work, Try taking the carrier off, put a block on the ground stand the axle and carrier straight up and slam it down in the block it should break it loose.
I live in north west AR, and had a bike with similar mods and ended up at 300/27.5. You should pull your carbs off and see what size is in them. Just keep an eye on your plugs you may want to start at 310 or 320 and work down from there.