factory exhaust manifold ID

so I need new exhaust for a 70 duster 340. going to reuse the original manifolds, question is if i go with TTi they want the factory manifold Id numbers. no problem getting the drivers side but the passenger side I`m guessing is located in the same area which is impossible to see, i can feel it i think though, so is my only option is to take it off and look. also any other recomendations for exhaust other than tti?