OK, here is what I have found so far...it seems that the '05 and newer Mustangs do use a balance shaft...the same engines that drop into the X are also dropped into the Mustang...I managed to find this web site with some great info on gears chains and revisions...you will need to scroll down a bit to the 4.0 SOHC section...there are 2 areas, one for the 97-02 and one for 03-08...in the second 4.0 you will see the Mustang listed right next to the Explorer which indicates that it uses the balance shaft like the X...so at this time I am feeling more confident about doing this swap...I am still doing more research...I would like to find some cam profile info too, just to see what the Mustang is using compared to the X.
http://www.rpmrons.com/fordtiming.html
Dave
I as well have recently completed the mustang 4.0 SOHC swap. I have put about 4000 miles on mine since installed. I have a 2001 2wd Explorer sport manual trans and installed a 2006 4.0 SOHC mustang longblock from an automatic.
I changed out all the front accessories, intake, fuel injectors/rail, wiring, exhaust manifolds. I saw some people mention the oil pans were different, I compared and they looked identical so I am using the Mustangs.