Internet Archive Exclusive ((full)): Tarzan 1966

The "exclusive" you're referring to is most likely the 1966-1968 NBC television series Tarzan, starring Ron Ely. The Internet Archive (archive.org) hosts a significant, fan-preserved collection of this series, which is often considered "exclusive" because:

Have you watched the 1966 Tarzan exclusive? Did you spot the continuity error in the third act involving the hunting knife? Let me know in the comments below. And if you have any leads on the missing second episode, you know where to find me. tarzan 1966 internet archive exclusive

If you’d like, I can:

Is it legal?
The Internet Archive hosts these as preservation copies of orphaned works (no clear active copyright holder pursuing distribution). However, technically, the series is still under copyright. The Archive responds to DMCA takedowns, but the 1966 Tarzan has largely remained untouched due to its "abandoned" commercial status. The "exclusive" you're referring to is most likely