Any thoughts on how much it'd cost to restore this rig?

If you can and do the work yourself, cost way less to restore it than buy one new. Especially a 4x4 ... altho, it's important the shell is in good shape ... other than that, it's sweat equity and parts ... and it's exactly how you want it...

Think $100K+ for a new 4x4 Tiger, for example, then decide.