Re: 3.9 or 4.1 ?
You wont get a 3.9 in an X series. They are 3.3l or 4.1. The 3.9 and 4.0 began with the EA's.
The 4.1 EFI system in apparantly really crap and hard to fix if it goes wrong.
Twin Cam EA falcon
SWB Ford Maverick