For the 8.2", is it 3.08 and numberically higher that use a different carrier , or 3.08 and below that's different? Follow that? :-)

2.56 and lower numbers for the 2 series, and 2.73 and higher numbers use the 3 series. That is for the 8.5, but I am guessing the 8.2 would be the same here.

3.08 and up use different carrier than 2.73 and down in the 8.2"... just did this swap about a year ago. (2.73's to 3.73's... thanks Freddie AKA: BigGearHead)

The 2.73 and other 2 series gears fit the 2 series differential. The 3.08, 3.36, 3.55, 3.73, 4.10 and others fit the 3 series.

Excellent, thanks! I suppose the posi units don't interchange? My '68 has a 2.73 posi in it. The posi is good with good breakway torque, but they're 2.73s...

One other question: Someone told me the 8.2s in Buick/Olds/Pontiac is different. I thought they were all the same, no?

no.

The parts out of a 2 series posi will fit in a 3 series posi case.