Its actually quite simple. The speech files in World Cup 98 are the same format as FIfa98 - PBK. When you originally set up WEd (the WC98 editor made by Chau which is basically an add on to FEd 98) it should merge the two commentary files so that players that are common to both games are now commented in Fifa 98 that werent originally but were commented in World Cup 98.
Furthermore, there are players in World Cup 98 that are not in Fifa 98. Just fire up WEd and go to the player screen, which is exactly the same as in FEd. At the far right hand side, after the column which is called 'Tac' you will find that you will be able to drag open a new column called 'index", this is the index no. or pbk file no. of that player. All players have these index no.s whether they are commented or not. Simply note the name and index of the player you wish to be commented on on Fifa 98. Go to the commentary file of WC 98 and copy the relevant pbk file. Rename it to the index no. of an uncommented player in Fifa98 and place it in the commentary file of Fifa 98, having already renamed that player in FEd 98 to the name of the player you are copying from WC 98 and saved it and there you go, a new player with commentary in Fifa 98!
There are a load of Iranian, Tunisian, Saudi players etc which are not commented in Fifa98 which are commented on in WC98 and also many of the past greats such as Maradona, Jairzinho, Rivelino, Meazza, Riva etc.
Furthermore, I discovered that the commentary file in Fifa 98 itself contains a lot of players commentary which are not included in the game. I assume these are players from Fifa 97 who were converted in a batch process and left lying around in the commentary file when the game was made. I have made a list of these names and their index numbers as a txt file and can e-mail them to anyone who wants them.
The actual process of renaming files is very simple, what frustrates me from making a great game even better is I dont know how to either create new pbk files or convert the later .str files used in later Fifa editions into pbk files. If someone knew of a way to do this it would be absolute heaven!
Each file is in the format Pxxxxx.pbk where x is a number. They must always be of five digits being made up of zeros if necessary for example index no. 390 would be P00390.PBK.