Hi arcage i am in Hawkes Bay , i run my car on 96 , you don't need to worry about addatives to replace the lead in the fuel as your has hardened valve seats, as for the engine # your cars # ,if it is the original block will be on the top left front as mine is on my 39 desoto , the 39 plymouths should be also if it is the original , as i said i have yet to see the car in question , personaly i have never heard of a chrysler, plymouth, desoto or dodge with the engine # on the rear , but we can always learn some thing new every day