If the fixtures are still in good shape, aside from the ballasts, I would recommend the 8' LED tubes, especially as it sounds like you're getting a reasonable price on them. If you're worried about them being too bright, you could start off with just a single tube in each fixture, and go up from there.
The only caveat with the 8' LED tubes is that some of the earlier generation bulbs weren't rigid enough, and started to droop, then fell out of the sockets. As always, try to buy quality.