Now by the looks of this chart the A-998 was fitted behind the 318s.
Here's another question: Being my '89 D100 came with a 318 would this make the transmission behind it a A-998 instead of an A-904? I know for a fact it is a non-lockup transmission.
No it is a lockup version or it won't have that electric plug in switch on the back of the front case. They switched to having the computer engage the lockup somewhere around 88ish