iPod classic shows content on macbook, nothing on the device

After doing a Restore, the default setting is to use Manually manage music and videos. If you want to use automatic syncing, you need to set it to Sync Music. Select the iPod in iTunes (click its device button on horizontal bar) to show its settings screen in iTunes window. Along the left side (in the sidebar), under Settings, click Music. To the right, the iPod's Music settings screen is shown.

NOTE: For anyone else reading this, any songs on the iPod that are not in your iTunes library will be lost.

Checkmark the box for Sync Music. If your iTunes music library can fit on your iPod, you can use the option to sync Entire music library. Otherwise, choose the option to sync Selected playlists, artists, albums, and genres; then make your selections from the lists below. Click Apply to sync your music library (or selected portion of it) to the iPod.

iTunes shows all content on the device

If you are saying you are looking on the device in iTunes, not looking at that content in your iTunes library, please post back with any other details...

On the iPod's Summary settings screen in iTunes, checkmark Enable disk use and click Apply (if that setting is not already enabled).

The iPod should appear on the Desktop or in a Finder window. Right-click it and Get Info. Do Capacity and Available look about right, for a 120GB iPod that has about 70GB of content loaded?