Bolt Patterns
 

Does anybody know if 1990 wheels will fit on a 1984. I am looking at used Millie Miglia Cup 1 that are the right size, I am just not sure about the bolt pattern?

Bolt pattern should be fine. You need to look at the offsets. 964 offset is 52mm (Mille Miglia's may be that or close to that). 89 and earlier 911's are, for example, 7x16 Fuchs 23mm, 8x16 10.6mm, and 9x16 15mm. You need spacers to make up the difference between your early offset and the later 964 offset.