I think those D'Addario sets are roundwound and are meant for 'modern' 6 string long scale basses which are tuned B-E-A-D-G-B(or C), whereas the normal tuning for a Fender Bass VI is EADGBE, and also it's also a short scale instrument.
I think Fender still make a suitable Bass VI flatwound set, although my mate who plays bass in my band tried a set of these on his 1964 Bass VI and the bottom E wouldn't tune right and sounded dead...
Anyway, best of luck!


