I just bought a '86 Grand National from a friend of mine...

Upon the first power brake burn-out, I noticed I have "the one wheel peel deal" goin' on (man that sucka smoked!!!!)
The car has a 8.5" 10 bolt w/a open diff. and 3.42 gears. I have a 2-series diff out of my '76 camaro that's a posi(has a preload S-spring) is it possible to just switch the guts???(spider gears,clutches, cross shaft etc...) Or should I buy a new unit??

that 2 series posi unit won't work with the 3.42 gears.
you might have a posi in the car, but it's burnt out. look at the option sticker on the bottom of the trunklid and look for the G80 code- which means posi. if it is a posi unit, it can be rebuilt with new clutches and what not.

and welcome to the world of the turbo Regal..

I did do a little diggin' and the car came w/a lame leg.

I know the entire 2 series carrier won't work with 3 series gears, just wandering about switching the internals of the 2 series w/the 3 to convert the open to posi.