in too deep: trying to go BBP on a 68 barracuda and its going.. poorly.

First you need to inspect what you have to order the correct parts. If it is a stock a body 8 3/4 it will measure 52 5/8 inches on end to end of axle housing so take your axles out and remove the drums and backing plates and measure. If it is this size, then purchased Dr diffs stock A body axles, your 3rd member should have 30 splines for the axles. you will need to upgrade the rear drums and backing plates, brakes to 10X2.5 size. you will need to choose what type of rear axle bearing you wat to use, sealed green or factory tapered, because it will matter if you need to remove the spacer between the axles in the 3rd member on the green bearings. I'm sure you will hear various other options. enjoy the car.