As I work at autozone I'm going ot be taking advantage of my discount for parts but I have a few questions.
Are gabrieals any good? Light offroading, but I generally drive like a jack ***. I was going to use the load bearing or the max controls.

I have the quad shocks, if that helps.
Also do the coil springs have a habit of going out becuase both my 89 and my 91 sit low to the ground in front.

I want to set the front wheels forward a tiny bit, is that even possible? I want the truck center of gravity to be set back a little.

How hard is it to drill the holes for front leaf springs?

 

I do not believe that that manufacturer makes a shock for dual configurations. I think they only offer a shock that is valved for single shock configurations. If this is true, by adding another set of shocks will create a pretty stiff ride.

Yes, all springs fatigue and a lower ride heigth and less weight capacities will result.

Not sure what you are trying to accomplish be increasing the wheelbase.
Since these are 4x4's you will also affect the breakover angle by lengthening the wheelbase.
If you are looking for weight transfer or something, you may be better off bringing the rear axle foward. This will also help with breakover. The downside is that it makes the departure angle worse than it is already.
You are considering Gabriel shocks, so you do not have a giant lift kit right?

The coil spring front end is way more desireable than leaf springs.
Lighter, smoother ride, better handling, better flex off-road.
Many guys are converting leaf sprung axles to a coil spring for the above reasons, heak look at the new Super Duty, even manufacturers did it.
Can't see any good reason to swap out a good system for leaf springs.
Is it hard, not really, but requires more than just drilling holes. Gotta weld up some spring perches and fab up some hangers and pivots.
Pretty sure even the guys going to solid axles are leaving coils up there.