This is what the 3.9 looks like without the Lincoln LS wrapped around it. There's alot of stuff hanging down in front that looks like it will get in the way.
The Rangers with the most room up front are the '98-up 2WD with coil springs. '98 was the first year for rack-n-pinion steering and the coil spring fronts are 4" wider between the upper control arm mounts. With a few mods there's enough room for a 4.6 dohc.