In 2016, the Mapes brothers found an assortment of Marvel Productions cassette tapes containing dialogue recorded in the summer of 1984, principally Season 1 of The Transformers. Deleted dialogue from those tapes is available on the Transformers At The Moon YouTube channel.
At the time of the recordings being found and made available, only one episode had a complete storyboard set available: Heavy Metal War. Animatics utilising the deleted dialogue from that episode were created and presented by Chris McFeely for TFNation 2017.
Since then, the number of full episode storyboards available online has grown to seven. Including a second episode for which a dialogue tape is available: S.O.S Dinobots.
To view the scenes in full context, head to: S.O.S Dinobots storyboard viewing gallery
Below is the video containing deleted recordings, along with the relevant storyboard pages and time indexes.