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.

Plum forgot about the B&T possibility, thank you.