[Rownbike]

Hi all,
I pulled the tranny out of my '69 today with the intention of replacing the seals on the rear case. (Truth be told, I really had to pull it because the speedo gear fell in while I was was trying to clean up a leak from the speedo output )
Anyway, I had thought that it was the original tranny but now that I can see the VIN on it, turns out it's not. Now I'm trying to figure out exactly what I've got. I've gone around the internet trying to figure it out but there seem to be a couple inconsistencies in the numbers so I need some help.
Here it is:
Casting #: 3925660 68-69 M20/M21 Good so far
Date code: P8T27 Dec 27, 1968 Is this produced in '68 for a '69 car?
VIN: 28U133454 From a 1968 Bird?
Tag #: 9798974 This is the confusing part. From what I can find, that codes for an M21 from a '69 Firebird.

It doesn't matter all that much, but I'd just like to know what the heck I've got.
Thanks,
Mike