differential upgrade

[naloleal]

I'm looking to improve my performance on my '66d100, but need some help.

How can i tell what my current gearing is, and whats a good set to look at? I do most town driving with the occasional trip on the freeway around 65mph. Right now on the freeway my tach reads just about 3k, maybe slightly above it.

Craigslist has a few different differentials in my area, but not sure what years and models will fit

[Hobcobble]

If it is known to be the original differential, you can look at
your VIN tag in the door jam for the ratio.
John