Mystery vibration at 25 mph can't be diagnosed. It's not the front end!

Yup, I'm with Mopar Tim. The vibe on acceleration at 25 mph or so points a big, flashing red neon arrow at the ball & trunnion front U-joint. You can still get the parts to overhaul them, but it's an expensive nuisance, and finding the knowledge to do it right is even harder. Instead proceed this way.