Marvel Team-Up #65-66, 69-70

Marvel Team-Up #65-66, Spider-Man and Captain Britain Pinball: This one actually isn't an X-Men crossover, but does introduce Arcade, a killer for hire who traps people in deadly funhouses basically. Anyway Peter Parker gets Brian Braddock (the newly minted hero Captain Britain) as a temporary exchange student roommate, and then discovers he is Captain Britain when there is a misunderstanding, a fight between them, and Arcade captures them both. They escape. (Also, Brian doesn't figure out the whole "Peter Parker is Spidey" thing).

Marvel Team-Up #69-70, Havok-in-a-Can: Havok and Polaris are attacked by some of the Living Pharaoh's goons and Havok is kidnapped. Polaris calls the X-Men who don't respond, then calls Beast for help, who runs to the X-Mansion to use Cerebro to find Havok. But, it doesn't matter much cause Spider-Man notices shit going down, rescues Havok, but then Havok gets put in a sealed device to superpower our villain back into Living Monolith (again). Thor and Spidey team up to take him down and rescue Havok.

X-Tra Notes: These are pretty unimportant, but it does explain why Beast is going to the X-Mansion in the next Uncanny comic.