There isn't any difference from car to truck for Chevy/GMC. Could it be that the "K" that you're seeing is actually an "H"? Sometimes those old castings can be hard to read, especially if they're a little crusty with road crud. As far as the main trans goes, there are diffences between the O/D version and the standard, mainly it's in the extra holes for lube and the reverse lockout mechanism. As long as it's a GM trans, it will be a bolt in, no need to mount the O/D unit to the original trans. Check out my pix from my signature on the bottom to see how mine's setup.
