By STRECH (ImpalaSSForum.com)

Is it an SS or a Clone?

  *  Wx3 code on the SPID sticker on the trunklid.
  *  There is also a decal on the drivers side cowl, just behind the front fender, bellow the hood hinge (on the edge of the firewall down below the left hood hinge). It will say WX3 right on it.
  *  Make sure the VIN on the SPID matches the VIN on the rest of the car.
  *  Driver's door sticker should specify the 17" wheels. should read 255/50/r17.
  *  Do a VIN check on it by someone that knows what they are doing and look it up in the production data base.
  *  Pull out your passenger seat it has a build sheet under the passenger seat with your car's vin, that should also have the wx3 code on it plus the day it was manufactured on. If that's number doesn't match your vin as well then yes it's possible that it's a clone!!!
  *  Just remove the center console. Look to see if the brackets that hold it are spot welded and painted from the factory. Can't clone that. They either have factory spot welds, or they don't.
  *  if you want to talk about exterior:
you also have the moldings over the wheels, the impalas have the nice painted thin molding around the tires, while the 9c1 has the ugly chrome and rubber like all caprices
  *  you also got the chrome lights on the caprice
  *  the chrome moldings on the door
  *  black stripe on top of the headlight lens that caprices don’t have.
  *  the rear tail light lens also have a very subtle black line in the cracks.
  *  go to a chevy dealership and ask for a GM vehicle VIS report that will tell you if its an impala or not.
if you enter the VIN at car fax it will tell you if it is a SS or a caprice.
  *  speedo will be 160

The unique items include--and I'm sure there are more:
seats
console (RPO D55)
other interior trim pieces

rear spoiler (RPO T43)
wheels/tires (RPO QAO/QBJ)
front brakes (RPO JB9)
grille
taillamps
wheel opening and rocker panel molding, and other exterior trim

Rear axle code for WX3 (found on axle itself) is unique, with standard limited slip/axle ratio combination (G80/GU4) - and axle is wider than the "other" rear disc unit used on 9C1

Suspension spec (FE4), including original deCarbon shocks, hard plastic front sway bar link insulators, and unique front and rear springs.

Driveshaft was specifically balanced for higher speeds

PCM flash was unique
the trunk switch is in the glove box.
Impala ss gets a sentenial lighting with Automatic Interior and Headlamp lighting.
Impala ss gets factory cruise control.