We are Purring Pumas, a San Diego, CA based supplier of Puma parts. We have an extensive inventory of new, Original (N.O.S.) and used Puma parts from Brazil. We understand you would like to install a jumpseat for a child on the rear section of the passenger compartment. While there may be enough room there for a small child, there is no factory seatbelt attachment in that area. Other safety considerations may came into play.
I would strongly advise against this. The fiberglass in the floors of Pumas in the rear is fairly thin and not strong enough to attach a seat securely. Always consider the possiblity of a collision when modifying any car. I would not want to have my kid back there in the case of any unfortunate events. The Puma is a Two seater. Keep it that way.