I think we may have a semantics problem here.
The wheel well is the opening in the TM sidewall and floor. The upper half of the tire lives in this opening. TMs originally had square wheel wells. Sometimes around 2001, the shape of the wheel well changed to half-round. A couple of our more enterprising members figured out how to convert their old square wheel wells into round ones. See, for example, Rick Newcomb's excellent writeup at his site
http://home.comcast.net/~trailmanor/whlwell.htm
In this case, the wheel well liner (aka fender liner) is made of aluminum sheet, bent into an arch and backed by expanding foam.
Today you can buy wheel well liners from the factory. The wheel well liner is a curved piece of heavy black plastic. You can sort of see one in the TM parts catalog as part number 27041, where it is called a fender liner (as opposed to wheel well liner). I don't think you can install these liners in an unmodified square wheel well, but I don't think that is what you are trying to do, so you should be OK.
Maybe I am running in the wrong direction here ...
Bill