Can you further clarify exactly which part you are referencing? Does 'rear' refer to the differential bump stop? or ??
PS. My car is a '69, and '68's may be different, but the differential stop bracket on my car seems to be attached permanently to the floor reinforcement and was primed/painted when the floor was done.. ie.. so mine has a mix of primers (not much color overspray in that area)... If this is what you want to see, and my '69 would help, I can post a pix...