I know there's been a bunch of threads on time travel, but I'm looking for more specific time travel fic recs... Namely, where both Buffy and Spike travel back in time to when Spike was William (can be 1880, or anywhere near that year). I don't want Buffy/William, although William may have a crush on her or something, but definitely Buffy/Spike. Bonus points if a point in the story is that Buffy (in the end) loves Spike not because he is William, but for who he has turned into through the years. Thanks!

Guest
To Save a Lady by Slaymesoftly here at SR
Summary: Spike and Buffy are sucked into an Initiative time machine and find themselves in 19th century London. Somehow, pretending to be husband and wife seems to be the way to go....

Foreshadow 1 : Grief, Despair and Hope by Alexannah
Spike has to face his past when he and Buffy are sent back to his first night as a vampire; meanwhile, the rest of the gang try to find a way to save a human being controlled by the Hellmouth he tried to close.

This is a bit of an odd one and William doesn't feature. I love the time travel bit but I must say I think the rest is pretty weak. The first part though is different and I think interesting enough to give it a read as it is a short fic. As far as I am aware none of the rest of the intended series was written but this is complete.

I don't know any other ones where they both travel back together, apart from To Save a Lady but that has already been suggested.

Imitation of a man by DarkApple.

This one is set in 18th century so a little earlier than your specs but give it a try, it's a fabulous read -- Lost in Time by Spikeskat http://spikeskat.rogue-poet.com/lostintime.htm