You should be able to reserve a group campsite at gold bar, which would be worth while dollar wise if your trips more then a couple people, and take some stress out of finding a camp site late at night when your tired.
One other option could be to camp up at Dewey bridge if coming from that direction, at least a better chance of snagging a site if no reservation, can also still camp for free across highway from Dewey I believe. Don't even try on week end though. It's at least an hour to potash from there, maybe a little more.
" I wish I were a headlight, on a North bound train..."