Vibration at 65 mph, E-150

1997 Ford Club Wagon (van)
5.4 liter engine, 110,000 miles.

A moderate but distinct vibration at 65 mph.
A general vibration of the entire van.
Moderate vibration in steering wheel.
0 to 60 mph no problem.
Starts at 62 mph
Maximum at 65 mph
Stops at 67 mph

Tires 6 months old.
Had tires re-balanced with no effect.

Same vibration driving steadily at 65 mph,
Or accelerating from 60 to 70 mph,
Or foot off the gas from 70 mph to 60 mph.
Steady as a rock above 70 mph.

What kind of shop do I take this to than would know how to diagnose vibrations?

I would check the driveshaft U-Joints first. One may be starting to sieze or very loose.