You really need a script for this. Is there a list of what files use what filenames? I have a rename script that I use in production, this is a modified version that will accept an input and rename selected files based on that. You could enumerate as many variants as you needed.
#target bridge
if(BridgeTalk.appName == 'bridge'){
FT = MenuElement.create('command', 'Rename', 'at the end of Tools');
FC = MenuElement.create('command', 'Rename', 'after Thumbnail/Open', this.menuID);
}
FT.onSelect = function(){
Renamer1();
}
FC.onSelect = function(){
Renamer1();
}
function Renamer1(){
app.synchronousMode = true;
var thumbs = app.document.selections;
var newName = '';
var newNameU = '';
var Title = [];
var counter = 0;
var variant = ['a', 'b', 'c', 'd'];
try{
newName = prompt('Enter part number');
if(newName != null){
newNameU = newName.toUpperCase();
for (var a in thumbs){
var selectedFile = thumbs.spec;
Title = selectedFile.name;
Title = (Title.split( '.' ))[0];
thumbs.name = thumbs.name.toUpperCase();
thumbs.name = newNameU + variant[(counter)] + '.jpg';
counter++;
thumbs.name = thumbs.name.toUpperCase();
}
}
}
catch(e){
}
app.document.refresh();
app.synchronousMode = false;
}