I have answered the OP's question. Most seem to agree. Now we can get into a long technical discussion if you want to but will be off topic. Like for instance......the door bolts are UNF to be able to quickly tighten after adjust. Not for strength. There are lots of greater stress places on the truck and they use UNC. There is no stress on door hinge bolts/threads when it's closed. When it's open, it is cantilevered, probably weighs 60-80-100 lbs and we lean on it. All those bolts are plenty strong enough for that, UNC or UNF.
Here is the reason we don't need to get into a strength discussion regarding our trucks. Gr 5 vs Gr 8, fine vs course and all that.
For example: using a 3/8 bolt. Using Shear as it is 60% of Tensile. using Gr 5 steel.
The course thread shear is 4985 Lbs
The fine thread shear is 5860 lbs
So 6 door hinge bolts will hold 30,000 lbs. 3 bolts is 15,000 lbs. So maybe the fine threads were actually for adjustment. Maybe the pin is weaker than the bolts!
After about 4 threads engagement, the stripout is as strong as the shear.
In a bolted assembly of two plates with a bolt and nut, the threads should be "below" the shear plane(the mating plane between the plates). So that the unthreaded shank passes thru the shear plane, if possible. But again, not necessary in our applications/stresses/vibrations/usage. Needs perspective.
Fine thread hardware are harder to find sometimes.
The extra strength, which depends on the application, is not needed in our trucks unless as stated in my answer to the OP and others who have responded.
If a person wants to use Gr 8 and UNF threads it's "fine", this is just a reference for those who don't.
Stay cooped up and wash your hands boys.
