My 60ft time was consistently 2.6/8s didn't matter what I did but in my old Saff the 60ft were low 2s and I was gettin the same terminal with lower power.

I stopped bothering to run it because it was so frustrating all that waiting and pushing and getting that!! And it was the same on the road in the end I would just big revs and drop the clutch hence getting the option to put the 3.9 in it

The diff is fine, I think I might have fixed the problem and will get some better times next year.