It depends on your riding style, but for a Loaded board, I'd suggest something like Paris brand longboard trucks or Randal brand longboard trucks.
My personal favorite longboard trucks are Paris trucks.
Longboard trucks can be bought from any stockist of skateboarding equipment or from online retailers such as Amazon. They cost around forty dollars for a pair.
Absolutely not, it is all preference. Some people have loose trucks or tight trucks; also experiment with bushings, they will affect the ride greatly.
yeah, you can get them from Tensor
You should always have the same size trucks
loose trucks and a wide board
Buy wheels, trucks, and a deck and screw them together
yeah, you'll need risers
No, as a matter of fact, tightening the trucks all the way is entirely the opposite of what you want to do. If you tighten them, turning will become much harder, because the trucks will be very unflexible. You want to loosen them until you find the perfect flexibility you need.
Yes, just swap your bearings from skate wheels to longboard wheels, its all the same.
The shape of a longboard was invented before but the trucks and wheels were small like those of a skateboard. Early boards didn't have pop.