Is it necessary to replace the crown wheel bolts on 8-3/4 ?

Unless he knows they're left hand thread, he'll likely need at least one.

I changed lotsa hi/po, regular rearsets thru the decades, seldom changed bolts, never ever have had a reason to regret that decision.
haha, that reminds me of a funny situation when I was removing them, happened to be about 2am and cold and I wasn't fully alert. Yes I knew they were LH thread, so I was undoing them with a ratchet and every time the ratchet eased up to finger tight I pulled it off and started undoing with my left hand. However I couldn't work out why they were not coming out and why they kept getting tighter. Back on with the socket and started undoing again, same deal, went to finish off by hand and same thing happened! Then realised what I was doing - the left hand was automatically going the normal way while the brain was asleep. Had to laugh at myself.