Need to ID a Transmission

Hey folks,

I was able to identify the trans I have in my Duster,

It is a: #4028877 - 1978' 318/A904 (standard without lockup)

Unfortunately I only have info between 1969-79

I found a A904 series tranny in a salvage yard it was already pulled out and stuffed in the back of late 80's work van. The serial number on it is #4505170
I tried looking up the serial number and only found one a brief description on one website.

#4505170 1989 Diplomat' A999 Lock-up, some 3.9 ltr vans/trucks.

I do not know how accurate that is but I need to know if this is something worth haulin' away and would be an easy pick as it is just laying there... mocking me.