Climb under the car have a looksy at your unis .there should be a C-clip thats removable .remove these and the uni sould pop out with abit of help .....check the holes were the uni goes in so its not ovall .if its ok order the unis from a truck dealership they should be able to size something up for you iv done a few unis myself .
Or your local repco should have what you want or beable to get them .............Have a read of your manual if you have one or a datsun manual of some sort may have more info on unis int diiff section hope this helps