Ok, this is an opinion based upon years of trial and lots of error. Weather you are a hardcore nut or a weekend wannabe, doing mods like coil conversions are not for everyone and doing research on the web will get you all kinds of wacky rude (not me)responses.

What I have found is that.. for the crowd that is SOA or wants to be, axle wrap is a huge problem. Solution 4 link done with correct geometry, spring rates and dampening (shocks). Next center of gravity, is your rig square or under, meaning can you afford to go softer, taller on suspension without going wider and longer?
Measure outside of tire (side to side) to outside of tire, then measure how tall your rig is or will be with the desired lift... if your rig is taller than it is wide, your over-square and are asking for disaster. If it is exactly square or under (with the new lift height) you should be ok.

If over-square, less lift or wider axles (wheel spacers/wide off-set wheels don't count) is the only solution.

Next, ultra almost silly "flex" is more for show and less for go. 10" of travel is excellent. With leafs 2" up and 8 down is close to real, coils 5 up 5 down is first rate. More is really not needed.

Now, front or rear?

Rear coil conversions stop axle wrap and if done right will allow the rig to traverse walls and ledges that were a hopping, axle snapping nightmare with leafs.

Doing the rear allows for a simple wheelbase stretch that adds to trail/street stability that cj's/yj's and Tjs can only dream of. It requires relocation of the fuel tank.

Rear:
by keeping the leafs in the front and coils/4link rear you keep very streetable stability and steering geometry intacked.

Front coils with rear leafs?
I still ask why?
If someone came up with a reason I could respond better.
Here goes...
By doing it that way, you keep axle wrap (soa and soft spring sua), then add coils to the front which adds very uncontrolled spring "unload", add more hassles to steering geometry (track bars and less availability for high steer)
Adding to likelyhood of bumpsteer and poor handling. With a stock width axle and narrow Cj frame a short track bar (longer is better) is inevitable. Ick.
Adding unloading, steering issues, softer than leaf spring rates, square or over-square problems makes doing a front coil conversion a rollover waiting to happen.

With stock cj or yj tj axles room for links and proper locations becomes a problem. Adding loads to frames that are 18 years and older (cjs) where they never had loads before is a obvious problem. Doing these types of conversions on yjs or tjs works better and lasts longer.

I suggest minimum of 64" wide (wheel mounting face to wheel mounting face) axles 66"-68 is best.

Spring under? Is there a problem with the ride? Do you think coils are the answer? Flex? Have you explored all the options? Like loosening leaf clamps, shackles too tight, lube between leafs, incorrect shocks/valving?
Reverse shackle?

I would like to know the thought behind a front only coil conversion?

The front coil rigs we do at the shop where I work are coil over with the shocks custom valved for the application.
These have less travel and harsher ride due to customers desire to keep good on street handleing.

The conversation can continue...

SD