the lower spec cars had 55amp alternators, then they jumped up to the standard 70 amp and the higher end ones had the 90 amp versions

if you are stuck you can always opt for the granada version which will bolt on if it's the correct version listed if you want it, besides, it's not as if you will notice any increase in getting hte 90 amp one but you may notice it with a 55 amp little diddly version

changed on about a year ago and the 55 amp one came out easy enough but the 90 amp one was much bigger physically and wouldn't slot through the same gap