if you want the suspension to be functional, there is no way a 4" can be done on a YJ without trimming the front fenders and rear quarters. look at how much clearence i have in the fenderwells with a 6" and 35"s. thats with only 18 lbs of pressure in the tires. if you run normal pressure on the street, you will have problems if no panels are cut. a 4" is designed to work properly with a 33" tire.you are right. its hast ever been done.
or wait, it has
since when is a MTR just for looks? its one of the most proven trail tires in hardcore wheeling and extreme crawling.
a 5" coil over will work, but i would rather do a coil setup with a 4 link front 3 link rear.to run 35s on the YJ since we are getting technical you need an 8 inch lift to clear with no problems with rubbing or anything.
even with a 6" he would be cutting a little or rubbing when her gets the suspension flexing
it was probably a TJ or JK. those are a little different than a YJ in terms of lift size.there is no way in hell im running 8"s. it will look way to ridiculous. ive seen 8" clearing 37"swith NO problem at all. Actually saw it 3 days ago when iw as speaking to the owner.
i know its on leafs, i have a YJ myself. the red one pictured is mine. about the only coil over conversion kit you will find is the fabtech, which still uses a spring over rear. for what it costs, you can probably get someone to build you a four link setup. but it may not drive as good. you can get a better leaf sprung kit from companies like rubicon express. another option versus the rough country (not my favortie manufacturer, but its hard to screw up four springs and a dropped arm) is a spring over kit with a 2" body for fenderwell clearence. it generally will give you about 5-5.5" of lift with the stock axle tubes. there is some cutting and welding that needs to go on, but its pretty darn basic. look into rubicon express. and remember, when going anything over 3-4" you will need a CV in the rear, preferably front too, and a slip yoke eliminator (short tailshaft kit).Leaf Springs - 1987-1996 Jeep YJ 6" Suspensionhttp://roughcountry.com/jeep_yj_6.html
I have yet to find a 6" coil over kit.