I am trying to determine if the Muncie 4-speed in my '70 GTO is replaced or if it is even a '70 unit.

The driver's side case has the number 3?52648 but also has a date stamp on the lower right that says 7-1-83. This is what is confusing me, and I am guessing that it may have been stamped by a rebuilder on that date.
The passenger side of the case has 3925660 then 3088336 and a stamp of POK238A.

Any help is much appreciated!

I am trying to determine if the Muncie 4-speed in my '70 GTO is replaced or if it is even a '70 unit.

The driver's side case has the number 3?52648 but also has a date stamp on the lower right that says 7-1-83. This is what is confusing me, and I am guessing that it may have been stamped by a rebuilder on that date.
The passenger side of the case has 3925660 then 3088336 and a stamp of POK238A.

Any help is much appreciated!

Rick, look for the VIN to be stamped on the case. It should look like a 20(1)(2) where (1) is the plant code, and (2) is a six digit number matching the last six digits of your VIN. As for the other numbers, the 3952648 is the casting number for the side cover. 3925660 is the casting number for a '68-'69 main case(further explained later). 3088336 is a patent number. As for the P(means Muncie), 0(means 1970), K(means July), 238(means you looked at it wrong or you typed it wrong or they stamped it wrong, it should be the day it was assembled E.G. 23rd or 28th), and the A(means M20, wide ratio). Now, as for if it's the correct transmission, if you have an early 1970 GTO, my guess is it's correct(if not original).