Diff Ratio recommendations

[1bigdog]

Hi All, new to this forum.  I just purchased a 65 Sky Convert. and am planning some running gear updates for it.  I was surfing the local craigs list  and found a couple of posi rear ends, one out of a 75 el camino with 3.25 ratio and another from a GN with a 3.73 ratio, both are 8.5" units.  I plan on getting a 200-4r tranny.  So a couple of questions:

1) which gear ratio would you all recommend for this car
2) which of these to rearends would be the easiest to install in the 65?

I don't plan on hitting the strip just want something that is nice to do some crusin around with decent performance and milage.  Currently the car has a 300 in it for a motor, but that could change down the road as well.

[WkillGS]

Neither rear will bolt right in since the control arm mounting points are different. There may be adapter control arms avail to put in the GN rear, but that adds a lot to the cost.  But maybe those are adapter control arms to put an old rear in a GN?

An 8.5 inch rear from a 71-72 Skylark or cutlass are the ones to look for. Gears are easy to find for those.
Or just get gears and a posi for your 8.2 rear.

[Brian]

Your car most likely has a set of 2.78 gears in it.  As Walt said, the 72 and older rears out of any GM A-body car will fit.  Keep in mind though that andy 68 and newer rear end is about 1" wider and will give you a wider rear track width.  I am with Walt--change the gears in you existing rear.  With an overdrive transmission, you can get a set of the aftermarket 3.90 gears and Auburn posi to go with it. 

[1bigdog]

Great insight, thank you.

[WkillGS]

Jim 'Monzaz' has extensive experience with the Buick rears. Check out his site here:
http://jdrace.com/
He's likely to have some used parts or can set you up with new stuff at a great price.