I don't really consider those songs to be fully fledged epics; they are just jams, and not very interesting ones at that...
The one I can think of is 'The Return Of The Son Of Monster Magnet' by Zappa which was about a side in length in 1966, but is every inch a filler track. It lets down the otherwise excellent 'Freak Out' for me. Thankfully, no other Mothers album had an excess anywhere near as excruciating as that one...
Love's 'Revelation' from their 'Da Capo' album in 1967 was a side long song too. However, 'Da Capo' is regarded as a one-side album, and it isn't the side with that on...It's a truly turgid blues jam that never lives up to the promise of the majestic harpsichord intro, again letting down a truly wonderful album.
The Rolling Stones' 'Going Home' was only just under 10 minutes, and was from 'Aftermath'. Again though, it's more of a jam but is more listenable than you'd suspect...