The Wilburys

Petty was bassist in his pre-Heartbreakers band Mudcrutch, I'd be very surprised if he didn't play all the bass on the albums.
Lynne plays Danelectro 6-string bass on a couple tunes, he plays it on most any project he produces, its part of his sound.
I'd also be very surprised if Harrison ended up with the Beatles' Fender VI.

"both in studio and live"

Don't believe the TW ever played live.

 

Jeff Lynne has definitely played some baritone guitar as well as bass on his own records. There's some cool baritone guitar work on his first solo record, Armchair Theater. I know that he was also pictured playing a Precision in Tom Petty's video for "I won't back down".

I also recall seeing some images of Dylan playing acoustic bass guitar with the Wilburys. Notably, a Kramer Ferrington.

 

Correct. They never played live.

They did discuss a tour, according to George, in which they were going to sing each other's songs, i.e., George would sing ELO songs, Dylan would sing Harrison songs, etc. Would have been cool. Roy's death put a quick end to any thoughts of a tour.

 

I don't think anyone has seen the Fender VI since Let It Be. It certainly didn't belong to any one member of the group. Probably stolen sometime in '69.

 

There was a report of a number of instruments being stolen from a storage locker at Abbey Road late in The Beatles career, possibly around the time of the sessions for Abbey Road. I don't know if there was an accounting of which instruments were taken in that incident.

I think the Bass VI might be featured in Andy Babiuk's Beatles Gear book, but I'll have to check. And I think it stands to chance that if an update comes out for the George Harrison Collection app for iPad, the Bass VI could conceivably show up there.

As for members of the Wilbury's playing bass? Here's a shot of Jeff Lynne with his Precision that he played on Tom Petty's video for "I won't back down"