Does anyone have a list/chart between the differences of diameters in driveshafts from engine to engine? 6cyl to 289/302 to 390 etc. Mustangtek website used to have something but it appears that page is MIA.
Seems to me that the earlier 6cyl were smaller and possibly the 65-67 260/289 as well, but trying to confirm...For '68 they were all 3" diameter until about March 1968. At about that time the 390 / 428CJ driveshafts started to have the bigger 4" diameter tube that still necked down to 3" at each end. So there might have been 45 days of transition period from maybe March - April 1968 when either could have been used because they are interchangeable.
You can buy a new driveshaft for any of these applications from Dead Nuts On. Prices are quite reasonable.