So I pulled the cover off the rear diff - here's what I found - 4.33 gears (39 teeth on the ring and 9 on the pinion) - which validates my seat of the pants guess that it was numerically higher than a 4.11.
Now I'm wondering if this was the factory ratio and maybe I'm not reading the code correctly off the rear axle tube. I was pretty sure that it was a ZH code, but the stamping fades out at the top of the Z and H, so maybe it's a ZR instead - that shows up as a 4.33 HD 4 pinion for a '68 Firebird...
If my PHS documentation would show up, maybe it would solve the mystery.
