48" (non-rotatable wheel version) deck on an x324. ~10 years old and runs great. Bolt holding the right hand blade sheared off the other day and had to replace the entire spindle/bearing assembly. Question is what is the proper way to remove (and reattach) the idler pulley on top of the deck? It is the stacked double pulley on the right hand side that the belt from the powerflow runs to. And more importantly, once removed (which I managed to do after a bunch of bruised knuckles) how to properly tighten that nut on the top of the pulley to reassemble it all?

I was able to hold the old one with a large pipe wrench to get the thing off, after a ton of horsing around and cutting away some of the old housing so I could get a good grip on it. Putting the new one on I didn't have that option so I just held the bolt on the bottom with a socket wrench and used a lug wrench to hold the nut on top. Not at all sure I got the nut on top tight enough, and with the way it spins (surprised it's not reverse threaded) I worry it will come loose over time. I cannot figure out any way to hold the bearing assembly firmly enough on the bottom to get a good purchase from the top side to tighten that nut. What am I missing?