I think it might be drive shaft related.

From a stop and slowly excellerating, the vibration begins with high frequency around 20mph while feeling and sounding like a bad u-joint. The vibes smooth out slightly and is felt though the seat until 40 mph where the vibration manifests in the steering wheel until almost 60mph. The vibration can be felt through the body at different frequencies with variations in speed but only shakes the wheel between 40-55mph or so.

The entire DS is from an 89; I put it in after my rear u-joint siezed. Could it be out of balance or have worn u-joints? Could it cause the steering wheel to shake like it does and be varied in frequency? I plan on rebuilding the whole thing soon anyway including the trans output shaft, I'm just looking for some input on it. I'll start with checking the wheel balancing and go from there to take that out of the equation. Also, how much if any, would large center caps through off the balance?

Thanks!