The three digit number is based on a combination of things (displacement, weight, dimensions, etc.). The difference between the 100 and 400 plate on the 70 series is the factory fender flairs. It seems trivial but somehow that width difference matters.Your license plate. It should have your prefecture followed by numbers, 100, 400, 300, etc. the numbers are related to vehicle size. Sometimes 77’s are tagged 100 or 400 with no rhyme or reason. If your tagged 400 I wouldn’t touch any suspension or bar work for fear of getting it tagged as a 100. Considerable cost difference in registration, road tax, jci.
Edit, based on your photos, your truck is a 100 series plate.
I may have a carrier in the near future for you if you want it.