rear main would be a good idea. (all gaskets/seals would be a good idea as mentioned above)
you could pull the oil pan and check your magnets, pick up, and do a bottom end inspection.
good time to do headers if you cared to.
all the basic maintenance would be mildy easier while it's pulled.
maybe clean it up real nice while you can reach everywhere and paint anything you care to so it looks all pretty when it goes back in--this is only applicable if your as anal as I am.
also, this is the best time to go ahead and stick a 1UZ in