DennisM, I'm using a 3.73/1 rear end in my truck, with 31" tires it makes 2000 rpms at around 50mph. Now You have 3,55/1 rear and 27" tires. Changing to 3.00/1 wolud be almost the same as putting the 31" tires. Don't You have a friend or someone elso that You may borrow 2 tires and put them in truck just to see how it goes, would be the same as swapping the rear, just easier and faster. If You like the results, them just return to the 27" and swap the rear or keep the rear and swap the 27" for 31".
