the op was made when there was only a system dump of 98.72.16. now that the fxz is out, you can easily make your own rom base...
get the fxz here:
get hashcode's original motoblur base here:
(motoblur-98.72.8-XT912.zip)
get koush's superuser here:
click "more", there is a download link
extract system.img from the fxz and then extract the contents of system.img (i use winhex) and put them in directory named "system"
add Superuser.apk to /system/app
add su binary to /system/bin (you can put it in /system/xbin but you'll have to edit the updater-script line that sets permissions for it)
extract the META-INF folder from hashcode's motoblur base and delete the 3 files "CERT.RSA" "CERT.SF" and "MANIFEST.MF"
zip the system directory and the META-INF directory (i use 7-zip with ultra compression), naming it whatever you like.
for extra credit, you can sign the package; or you can just disable signature verification in recovery.
