I'd look at the thickness of the clutch plate when you have the transmission out to replace the slave. It is possible the clutch was replaced before since failing slave cylinders plague all rangers. A few years ago I had to replace the slave on our 94 ranger. I thought since I was right there I would spend the extra bucks and replace the clutch. So, spent the cash and did the swap. But, I soon learned the new clutch plate was no thicker than the old one, and upon closer examination, I discovered the clutch and slave were not original to the truck, and had been replaced before, and the clutch was still good, so I kinda wasted the cash on the clutch.
However, I would definitely spend the money to replace the clutch master cylinder when you replace the slave. The clutch masters are also a weak point on the ranger, so do both at the same time, and view the bleeding technique video referred to on many of the threads in this forum, put out by precision or perfection clutch systems. The video is on youtube. A must view before you touch any part of a ranger system. If you want to buy parts, buy from them as they deserve our business for putting out such an excellent video.