rear gearing with a four speed A833.

Yes you are correct about fuel and oil control. And even though they are a big contributor I didn't want to mention them because I was talking about rpm. I suppose they go hand in hand but I still from an engineering standpoint. The less Times the engine goes around the longer it will last haha. I will mention though that even though oil and fuel control is better I have witnessed relatively fast engine wear from a Ford 4.0. 150,000 and it uses a quart every 1000 miles. It's in my brothers Mazda b4000 pickup. I told him to buy Mopar lol.