D100 Pickup question for you:

Let's do some math. If you have the 420, which I suspect you do, first gear ratio is 6.68. Couple that with a 3.91 rear and you have a combined ration of 26.12. Now looking at a car with a 2.66 first gear and a 3.23 rear, you have a combined ratio of 8.59. How high a rear end ratio do you have to have to get the equivalent of the car combined ratio? It doesn't exist. Even with a 2.76 rear you have a combined ratio of 18.44 or over twice the car equivalent. If you have the 435, which I doubt, the highest first gear ratio available was a 4.56 which coupled with a 2.76 still gives you a 12.59 overall ratio. It just isn't in the cards to get the equivalent of a traditional first gear by changing rear end gears.