The 904 build up article is from CarCraft June 1998 and shows an adpater plate being used as mentioned.
Here's a linkt to a page at javelinamx.com with links to the article a little ways down the page.
http://www.javelinamx.com/JavHome/articles/article2.htm
That's right, as mentioned AMC's with the Iron Duke 4 cyl had 904's with a SBC bolt pattern bell housing.
Those gotta be few and far between and difficult to find, but would be "slick".