early vs late 2004 frame difference

[anesthes]

So what is the deal with that. Early 2004 requires fisher push plates # 7159, while late uses # 7173.

I realize the change in 2005 for coil front end, but why the oddball 'late' 2004 frame change?

And how 'different' is the frames that really require an entirely different set of push plates?

-- Joe