Rusty rear end cups/trailing arm mounts - now what ?

[Green Machine]

The rear end cups/trailing arm mounts that the big U bolts go through look pretty thin and rusty on my 71 C20. They have the helper spring plate underneath and it has been my experience that the plates drain holes plug up and let the water sit in the cups and rust the crap out of them. I know I need to get thoses plates out of there and replace the big U bolts, but what to do about the rusty cups themselves ? Clean and ignore ? Have something welded on there ? Or find a replacement housing ? Whats a good price for a good used empty C20 housing ? Thanks