2007 F150 4.2 V6 with 225k miles. I've had truck about 5 years.
I have a noise in the front that sounded like a bad pulley. I've replaced all the belt pulleys and belt and still have same noise. Note that I've always had a little vibration around 40-50 mph, even after replacing U-joints and new tires.
So I wonder if the noise (and vibration) is possibly the harmonic balancer? Is it difficult to replace DIY? TIA

 

Have you tried removing the belt, running the engine, and then checking for noise and vibrations?

 

I don't see how the harmonic damper would cause noise unless it's wobbling so much it rubs the back side on the front engine cover.
same with feeling vibrations at 45-50 that to me sounds more like a possible slight misfire under load, not damper.
As suggested above if you remove the belt and run the engine and the noise is still there then it's from the crank (which is the only external thing spinning now) or from something on the internals.

 

are the dampers on these like previous years where the outer ring it attached to the center via bonded rubber? I've certainly seen those degrade and wobble around, rubbing the timing cover wasn't unheard of. I had one come apart mid dyno pull on my 4.6 and exited the vehicle

 

Yes that's sort of how these are, the pulley has a rubber isolator ring molded between it and the hub. I would think it would be pretty obvious to see if that was wobbling enough to rub?

Since this is an 07 maybe the op should check the crankshaft endplay to make sure it's not a thrust washer problem.

 

I removed belt, ran engine and no noise. Fan spins freely after shutting off engine. I guess all that remains in Power Steering pump and Alternator. Isn't there a way to test vibration and noise with a steel rod or something on the suspect device that then transfers the sound to the ear?

Note, it seems to be more consistent in cold winter and would go away after warming up for a few minutes. This sounds like a bad bearing in something that when cold, is contracted, and more room to make noise and wobble around.

 

As a possibility, it may be your fan clutch. I've read of a few people that had their fan clutch do exactly what you described, make a vibration and noise at a certain speed (rpm.) If you replace it, I highly recommend to use an OEM Motorcraft as more than a few have had issues with other brands.

Other than that, I would think the power steering pump or alternator or a pulley would make noise consistently that you could hear using the old school method of (while the engine is running) getting a long screwdriver, putting the end of the screwdriver on the alternator (or whatever) and putting your ear on the other handled end to listen. You hit the nail on the head with the suggestion of a long rod.

Just some suggestions...