For DOT tubing and fittings, any large truck parts supply store [Note: not all brass compression fittings are DOT approved, such as many sold at home supply stores].
On our MC-8, we picked up an air supply at the aux. air tank that is mounted in the top of the compartment under the drivers seat, accessible from outside the bus. The line from this tank runs to a pressure regulator and then to the throttle pedal assembly. From the throttle pedal assembly tubing runs to the engine compartment. At the engine compartment, this tubing ends at a T fitting. From the T fitting 2 pieces of tubing of equal length, one to the modulator on the transmission and one to the air throttle actuator on the governor. Only other tubing is a short piece from the throttle pedal assembly exhaust port through the floor.
No engine compartment existing air lines were altered or removed when installing the air throttle on our bus.
Several possibilities for tach sensor. It could receive signal from R terminal on alternator, a sensor on flywheel or a hall effect generator on an accessory drive. As was mentioned, photos would help. Jack