I've never been able to find another link to that fic.
Other Enemies by Chelle
http://dark-solace.org/elysian/viewstory.php?sid=119&ageconsent=okSummary:
(Buffy/Spike)(NC-17)FINALLY FINISHED!!!! This is going to be a series. It picks up where Enemies left off. Buffy almost murders Faith and gets scared so she decides to run away again and Spike shows up just in time to catch her and let her know he needs her help desperately. They embark on a road trip to Mexico that leaves them both out of sorts...
These 2 aren't NC17 but the first is a road trip.
New York, New York by Isabel
http://web.archive.org/web/20050213095155/http://vampires-kiss.net/fics/newyork.htm
Summary: Buffy and Spike are forced to go on a trip to New York together... For the sake of this world. A New York based sect is planing on bringing the Apocalypse upon the world, and they are the only ones who can stop it. But can they get along? R
http://web.archive.org/web/20050213094914/http://vampires-kiss.net/fics/newyork2.htm Remember New York? by Isabel
Summary: Sequel to 'New York, New York'. After coming back from New York all alone, Buffy tries to go on with her life, but her heart is not into it. She feels lonely. The love she gets from her friends, is just not the love she craves. PG-13
This one has them on the run together.
Battle Stations by VICNOIR
http://web.archive.org/web/20050213225010/http://vampires-kiss.net/fics/battlestation s.htmlSummary: Buffy comes to terms with her feelings for Spike as they hunt for/run from a particularly nasty vamp from Spike's past. NC-17
This story is WIP but updated often. Spike is very evil at first. To me pretty much in character for early Season 4. Slowly he is changing though now. Of course it has to do with being around Buffy.
A Gem of a Soul by spuffy luvr
http://dark-solace.org/elysian/viewstory.php?sid=3442&ageconsent=okSummary: Ever wonder what would have happened if Spike hadn't lost the Gem of Amarra to Buffy? If he'd won that fight instead? Warning, this story starts out very dark. Evil vampire, after all.