yeah I wondered the same thing Fishy but then whats the difference between the 66-72 and the 73-up ? since the kit was listed as being for 73 and up I figured this must be one of those little differences .
They probably eliminated the boot as a cost cutting measure. Do you have the o.d. of the wrong seal? If so I can measure it against one I have here from a 727. A lot of the time they changed things there's just a minor difference and sometimes you can use the older style part in a newer trans. and vise versa, but not always.
BTW: O'Reilly's has a pretty good website to look up parts on. It shows dimensions on a lot of parts so you can compare them to yours. I've had good luck with it.