I think the 2005 Sebring convertible seats would physically fit in the 1999 Sebring convertible. Would the power driver seat from the 2005 work in the 1999? I have a power driver seat in the 1999 now so the wiring is there. I'm not sure if the 2005 power seat would work in the 1999. It's a lot easy to unbolt them and bolt in replacements than reupholster. Already have quality covers over the 1999 seats.

 

There's one way to find out. I doubt rather seriously whether anyone on the forum has actually tried to do this, but if you are willing to give it a shot, come back and report your results.
There was a slight change in the floor pan for the 2001 convertible, but it may not have affected the front seat mounting.
The styling of the seats is a little different, so you won't get a perfect match.

 

From what I researched. They bolt up fine and the power seats work. What is different is the ABA system. I assume the seat belts and module would have to swapped from the Gen I seats to the Gen II seats to make it work. In "theory" it should work.