TAKE YOUR TIME AND YOU CA HAVE A VERY NICE RUNNING LITTLE TRUCK,, AND THE 3.73 GEARS WILL WORK JUST FINE ,, EVENTHOUGH THE PICKUPS CAME WITH 4.11 , HOWEVER THE 2WD 5 SPD TRUCKS CAME WITH 3.73 ALSO, IF YOU JUST WANT TO SAVE YOURSELF A LOT OF WORK JUST SWAP IN THE ENG AND TRANNY AND USE IT AS A 4SPD ( IT IS CALLED AND MSG-4T ) AND THEN WHEN YOU NEED TO TOW SOMETHING BIG AND HEAVY SHIFT IT DOWN INTO 4 LOW AND GO, THAT TRANS IS PROBABLY THE STRONGEST TRANS ISUZU EVERY USED ALLMOST BULLET PROOF, FOR A SMALL ENG,,AND EXPECT ABOT 70 MPH TOP SPEED WITH THE 3.73, AND THE BRICK DESIGN OF THE POSTAL TRUCK, I BUILT UP A TURBO ENG MANY YEARS AGO FOR A FRIEND OF MINE AND USED AN AUTOMATIC 3PSD IN ONE OF THOSE TRUCKS FOR HIS WIFE TO DELIVER MAIL AND NEWSPAPERS IN AN SHE LOVED IT , DROVE IT FOR A NO OF YEARS AND SOME ONE STOLE THE DANG THING WAS NEVER SEEN AGAIN BUT IT WOULD ACCERATE LIKE CRAZY WHEN THE TURBO CAME ON BOOST UP TO ABOUT 50MPH ..STEERING WAS SO LOOSE IT WOULD ACCEL FASTER THAN YOU COULD CORRECT FOR THE LOOSE STEERING , GOOD LUCK JERRY