What would be better for a SAS track?   Coils/Leafs

Coils would ride a lot better than leafs, they also flex better (if set up right)
Theres just quite a bit more geometry compared to leafs.

Leaf springs are cheap, easy to come by, you can fine tune them, and they are much easier to set up and install. Theres just not a lot to them.  Just spring hangers, shackle hangers, and shackles.

If you can pull it off coils would defiantly be the best up front.

Amilla

I have the same view as Amilla.  You can't top coils unless you go with Coil Overs, but leafs are cheap and easy. 

Im not to worried about the ride the GO tracker already rides like a tank with the setup I have now. (I cant see it getting any worse)

Im not a great fabricator by any means, but Im pretty sure with a welder and some steel I could knock out the leafs within a good weekend. I would like to run coils but cost+all fabrication    kind of steers me away from that set up. I was going to buy the calmini +3'' susp. for my IFS but with that price I can do the SAS. I still want to keep it very road worthy   and not just a trail king.

Coil overs is just a dream for my skills and pocket book

If I go with leafs, do you guys think I would be sorry that I ditched the IFS?

Been thinking about this myself. I have done some measuring and a stock sammy axle with springs is about an inch and a half narrower than the sidekick frame. The front frame rails will have to be extended some, but the fab work should be straight forward. Chances are you will be lifting the tracker some more as well, especially if you do a spoa. Problem is won't know how much until the job is finished. I think the swap would be well worth it. The front end will flex more than the IFS.

Unless you are planning on running tires that the IFS has problems dealing with, I don't think you will see much of a change.  I suppose it really depends on what type of wheeling you are doing.

If I go with leafs, do you guys think I would be sorry that I ditched the IFS?

I bought a SAS'd 4-door on 35" tires. They re-used the yota leaf springs (I'm sure to save money / fabrication time). My 4-door on 1.5" OME lift with 29" tires rudes MUCH MUCH MUCH nicer, and I think for sand or fire roads, it's the best way to go. The SAS on 35" tires really shines in the rocks, and did well at the Rubicon. I'm sure either would do well in the mud, but again each would have an advantage. The rotational weight advantage goes to the 29"ers, and the 35" would only "win" if the mud was axle-deep on the 29".

Mind your gearing. The most challenging part of owning a Tracker / Sidekick to me is gearing properly for tire size. If you're going SAS, you can go up to 5.71 in the diffs (and ignore the BS about 5.71 being weak - buy Yukon and they won't break). You can also do Kicker 3 (which is what I'm doing with the 35" tires).

I found an awsom thread on a SAS tracker  http://bbs.zuwharrie.com/content/topic,76103.0.html

Im going to start building the  toy axels , frame extension, and spoa brackets off the truck.  Once I finish everything then I will be taking one good weeken to finish it all up.  Hopefully!