There are two sets of head canon voice videos that I watched during my lifetime that I for the life of me I can't find anywhere.
First I'm going to start with the more recent of the two. In I'd say around 2023-2024, a channel for whom I cannot remember the name of uploaded 3 videos under the "If The Railway Series Had Voice Actors" title. Part one contained engines 1-7 I believe, part 2 contained many of the secondary characters, and the third and final part contained the Skarloey Railway characters.
The voices for the characters I can remember are as follows.
Thurl Ravenscroft as Gordon
John Fielder as Percy
Paul Winchell as Toby
Mel Blanc as Bertie
Vincent Price as Diesel
Candy Candido and others as the Troublesome Trucks
Eleanor Audley as Daisy
I believe June Foray and Sterling Holloway were also featured.
Now onto the second set of videos. These were uploaded around 2016-2018. Basically, these were voices for characters from the RWS/Model Series that didn't appear in the CGI series. I believe there were at least 5 or 6 parts. Most of the voices were people from Horrible Histories, but the main thing I remember was Weird Al Yankovic as Billy.
In conclusion, any help in this search would be appreciated.