Tiger Rearends
That be me.
Tigers came with 10 spline pinion gears. Dana switched over from 10 spline (coarse) pinion gears to 26 spline (fine) pinion gears in the mid 70s. Most trucks and cars have taller tires than Tigers and consequently many of them don't have 2.88s, let alone the course spline pinion gear.
The 10 spline 2.88s are getting harder to find. Best bet is to get them from other Tiger guys who have mistakenly converted to 3.07s or 3.31s thinking the problem with acceleration was the rearend gear, when in reality it's the close ratio transmission with the tall first gear.
Sunbeam Specialties sells the fine spline pinion gear flange, since that is all you can get nowadays.
Good luck,
Gary