Michigan Law. sorta interesting.
Lift blocks
(2) A person shall not operate a motor vehicle of a type defined in subsection (
that exceeds either of the following limits:
Vehicle Type Frame Height Bumper Height
Passenger vehicle............. 12 inches 22 inches
Other motor vehicle:
Less than 4,501 pounds GVWR... 24 inches 26 inches
4,501 to 7,500 pounds GVWR.... 24 inches 28 inches
7,501 to 10,000 pounds GVWR... 26 inches 30 inches
(4) Notwithstanding subsection (2),
a person shall not operate a motor vehicle having lift blocks between the front axle and springs, or with lift blocks that exceed 4 inches in height between the rear axle and springs in addition to those provided by the original manufacturer. Any body lift block shall be of single piece construction and shall not use more than a 3-inch spacer. Any suspension lift block shall use an alignment pin between the axle and the spring, and shall be of single piece construction. Spring shackle replacements shall not exceed the original equipment manufacture length by more than 2 inches, and coil spring spacers are prohibited. All steering components shall be geometrically arranged to function as original equipment manufacture. Welded pitman arms, drag links, and tie rods are prohibited.
All parts used to modify the original suspension or height of a motor vehicle shall be factory manufactured and shall meet or exceed the original manufacturer's specifications.
(7)
This section does not apply to a vehicle having a manufacturer's design which intrinsically precludes conformance with this section,
a vehicle with a GVWR of 10,001 pounds or more
so it looks like it is illegal for a truck that weighs under 10k, but not over 10k in MI if they are Factory made parts??