I have a messed up fender and one is up on ebay, but i have a series 4, and the fender says 89-91, or series 5, are they interchangeable, or do they have differenting moldings and don't line up with the regular?

 

Fender is the same except for the mounting hole to accept the different series mounting systems.

 

Plus the S5 fendor doesn't match the stock lines on the car and looks kinda funny

 

The fenders are about 99% the same. Just use the appropriate side moldings for what year your car is as those are different between S4 and S5.

I put a fender off an 87 T2 onto my 91 N/A. The only differences I noticed (and these may or may not apply to all situations, manufacturers can never decide how they want to do things):

The side molding on my 91 fender (closest to driver side door), was clipped into the fender. On the 87, it was glued on.

On the 87 fender there was no small protrusion to attach the last screw for the front skirt. It attached on the 91 fender right in front of the front wheels. The 87 had no such hole, but the skirt is tight enough that it doesn't need to be attached.

So, yeah, they're the same.

 

im am bidding on that same fender, so mabe instead of outbidding each other to death we should decide who gets this one

 

you can have it bro, ill be looking for another one in a few wekks anyways, its all yours