Well my 1994 ford ranger's clutch piston has gone bad and I have a 1988 ford ranger with a clutch is it possible to swap the two or no ?

 

They probably would switch out just looking at the parts from Rock Auto, but the actual part numbers are a little different.

With that said, using old used parts from another truck when it comes to the clutch, is not a good idea.
It's not the cost of the parts, but the amount of time it takes to install them, like having to drop the trans to replace the slave cylinder.
Even putting in the master cylinder is not easy.

You could use the bits from the 88 and they could fail with in a few months.

EDIT:
The master cylinder is very different, the 88 has a plastic flange that bolts in place, while the one for the 94 is held in place with just a spring washer.
Hard to say for sure if the slave is interchangeable, but you will want to put a new one in there anyway.