I believe that you were able to tell if a 68 was an SS or not if it was built in Canada.The Z03 option code most likely would be on the cowl tag.
I recently purchased a 68 SS convertible and from what I've found,an SS has to have Buckets an a console,special door panels with the SS badges,super sport identification on the dash.Outside,special Impala Super Sport emblems on the Grille,Trunk lid and Front fenders.Look for Caprice style tail and back up lights.
BTW Gene,the Z03 option was avaialble for the Sport Coupe,Custom Coupe and Convertible Impalas.
I hope this info helps,in any case enjoy the car!!!
