John,
Your ’73 will have two different size pipes in the tunnel. The larger one is the supply to the rear pump and the smaller is the return to the drain fitting in the tank. The ’71 should have two the same size for the standard 7 mm hose (999.180.030.50) and the 12 mm Norma Schellen (N-S) clamps (999.512.174.02).
I’m in favor of having the hoses continuous from the pipes at the tunnel to the first connection in the engine compartment. Most leaks are at connections and fittings. If you minimize the number of connections, you reduce the leak potential. The reason for the insulation on the hoses is they pass close to the heater waste hot air at the heater control valves. I prefer to route the two insulated hoses between the rear shock cross member and the firewall. There is a foam insulator there so it is easy to push aside for the hoses.
Flattery goes a long way but even without
this it is worthwhile to keep my brain functioning.
Best,
Grady