Duster Driveshaft length causing Vibration?

Gents, Thx for the feedback so far...I have also fully reviewed the Denny's driveshaft web site material from my previous research and found it very helpful.
I do intend to pull the driveshaft in the near future and re-asses the full set-up using your advice and what is posted at Denny's site. Others in my local club have worked with a shop called "Republic Diesel" in Louisville and I intend to engage their services in producing a new(longer) driveshaft and re-assessing if my Yoke is "O.K.?" (Anybody have experience with them?)
If anyone else has other ideas/recommendations, bring them on....In any event, I will re-post updates as I make changes..

THX-Scott (Bardstown Ky.)