I would agree with your assessment, the 3.9's sole purpose is to not look like the 3.8, even though it's still basically the same engine. I suppose it's not a bad idea either, considering the problems that the 3.8L V6s have had in the past. I guess I didn't catch on right away since I'm the owner of a car with one of the 3.8s that didn't screw up. 125,000+ miles on my '94 Thunderbird with a completely original 3.8L V6; no repairs, no blown head gaskets, nothing. For that matter though, my 4R70W tranny is entirely original too with no rebuilds or anything so I guess my car was one of the luckier examples off the assembly line. The only thing that did go bad on my car was the paint which really began to go bad in the past couple years but I took care of that and got the whole thing repainted; kept the color too, "Light Evergreen Frost" or so Ford called it back in '94.

Unless Ford's planning on putting more than one V6 in the F-150, I assume that you're referring to the usage of the 4.2L OHV V6 again in the '05 model year. I think that's the minimum engine that Ford can use in the F-150 because anything less, like the "new" 3.9L, would be too underpowered, especially with the weight gain that the F-150 experienced with the '04 redesign. I don't think it matters much anyway though because Ford's been leaning toward making a new V6 for heavier applications like the F-150, it's just that finances have restricted the development of such an engine. So, as a result, the 4.2 is still used in the interim simply because it's cheap and readily available but is still also a capable design. There is a prospect for the future though with the upcoming "Duratec 35," Ford's new 3.5L DOHC V6. The engine's already expected to be able to produce 245Hp and 240lbs-ft of torque but more importantly the design architecture is expected to be able to produce a new family of V6s. I've already heard someone on this forum mention the idea of a "Duratec 40" to be used for heavier V6 applications. The point though is that Ford will likely, finally, succeed in phasing out all OHV gas engines by the end of the decade.