wise2k

So, my 99 GS300 fuel pump went out and upon shopping for a replacement I came across a question as to what is the production date for my car. Apparently before and upto 4/99 pumps are different from those 5/99 forward. My car was made 3/4/99, and when I said that they said "oh, early production" we have one of those.
My question is, how much of a difference is there and does it really matter..? Am I better off getting a 5/99 or newer pump instead of the identical one (4/99 or earlier) to mine..? Or they are not interchangeable..?

wise2k

Help...anyone?