Normaly that ratio would be paired with an engine with much more torque than a 1.6 Pinto. You would not "sensibly" put the combination in a sierra as the engine would struggle. It may fell ok in the roadster.
However, you not going to have the power/torque combination to get the value out of that diff which is higher top speeds. And, realy, the roadster is not cut out for HIGH speeds and is more of a point to point acceleration and braking car.