Originally Posted by Jeff Wills

I've found that the flange dimensions for Shimano hubs are within a millimeter or two since the mid-'80's, so... if you want to use an 8-speed cassette, use anything made since 1994. This is when Shimano moved to 8-speed across the board. 8, 9, and 10-speed hubs use the same width cassette body and thus have the same offset (dish).

If you're trying to minimize the amount of offset (dish) in the wheel, go 7-speed. The cassette body is shorter. However, you won't be able to put a "normal" 8-speed cassette on it. (You could try "8 of 9 on 7", but that's a story for another day.)

Good reference: Sheldon Brown's Bicycle Frame and Cassette Spacing Crib Sheet