Greetings!

I have a 1982 euro 300d 5speed. the final drive ratio in the diff I believe is a 3.56. I want to get lower rpms while on the highway. the engine seems to be a bit strung while doing much over 75mph. I am considering replacing the 3.56 with a 3.07 differential from a later domestic model. The one thing im worried about is premature clutch wear while starting from a stop with lower ratios. Does anyone have any knowledge on this idea? thanks alot!

Greg