If you have both trannies to view, check the main case number on the thin aluminum plate which is attached to all of them. I cannot recall which is the 98+ case code desired, but I think I'd recognize it if you post it here. Look for something like "P8X" or a similar 3-4 letter code. There are many various items listed on the tag, only that I'm referring to is important.
The 98+ has one big improvement over older 4R's, and one fairly important change. You know about the mechanical diode in all 98+ models, but that's easy to buy and install in any model, back to the AOD's.
The case changed in 98 also(thus the requested tag code), before then the OD accumulator bore is a smaller size. The 98+ use a larger OD accumulator, and before then a sleeve is used with the accumulator IIRC.
The wiring did change for 99+, I think 98 is the same as 97 down. You can tell by the color of the case connector going into the trans. Is it white or black, are they the same color on your two examples? The wiring changed going through that connector in 99+ models, so either the harness wires have to be moved around, or that in trans harness has to be swapped(which is mated to unique connector shift solenoids(avoid changing that harness)).
