I personally don't like the coil conversion... not worth it. If you want coils, go get a TJ. Instead do a SOA... that will give you all the flex you want. If you want your YJ to ride better, do a shackle reversal.
Yea, D44s are all over the places... fullsize jeeps, scouts, broncos, F150/250, isuzus, etc. you should have no problem locating one in a junkyard if you know what you are looking for. But there are many versions of the D44, so you'll need one that suits your application.
1995.5 Isuzu Rodeo - SAS'd and SOA'd, sitting on 36x12.50 TSLs, D44 front, 14bff rear, locked by OX and Detriot, suspensions by Jeep and Chevy, high steer conversion, 5.13 gearing and Teralow in the case.