Over on his excellent blog comics legend Jim Shooter is discussing the DC/Marvel crossover stories and why the first JLA/Avengers crossover never happened.
In Part Four Jim Shooter refers to Dick Giordano's rebuttal of Shooter's Marvel Age column regarding the crossover and its failure to happen. For curiosity's sake, here is Giordano's rebuttal, as found in Flash #341 (1985).
I am so far unable to find Part 2 but it'll be in a DC Comic dated January 1985. If anyone finds Part 2 then let us know.
UPDATE: Success! Lee K. Seitz has found not only Jim Shooter's column from Marvel Age #19 but also Part 2 of Dick Giordano's article. Check them out here. Considering we're discussing company crossovers I think it's very appropriate that these articles are being presented by a blog crossover. Many, many thanks Lee K. Seitz!
UPDATE 2: Jim Shooter links to a blog with an overview of everything concerning the failed crossover that's public knowledge, including some of George Perez's awesome pencils. As it's such a fascinating read I thought I'd link to it too. http://marvel1980s.blogspot.com/2011/06/1983-jlaavengers-crossover-also-known.html
UPDATE 3: Many thanks to Nevermore, who informed me that Giordano's article is reproduced in the JLA/Avengers (2004) Hardcover Collection's Compedium. So this column wasn't the great find I thought it was but it was a pretty exciting feeling reading Jim Shooter's reference to Giordano's rebuttal and thinking "Hold on, I've got that!!!"
On a related note I thoroughly recommend Kurt Busiek and George Perez's 2004 JLA/ Avengers. I don't know if it would live up to Mr Shooter's strict requirements but I can say that it's a lot of fun and contains Superman wielding Thor's hammer and Cap's shield, Kyle Rayner charging his ring on the Cosmic Cube, Hawkeye stealing Black Canary from Green Arrow and many more such cool, fanboy-wish-come-true moments. Check it out!