This is a major fabrication project and not one to be started lightly. There is a guy here on the Stovebolt who has done it, and I expect he will chime in here and say don't do it.
The '78 to '88 Monte is the one that is considered a good fit for AD trucks. But what that means is that the track width is right to allow the wheels and tires to fit right under the fenders.
The Monte and its g-body cousins are not unibody cars, and actually have full frames. When you say 'clip' in this context you are actually cutting the front of both frames off and grafting the Monte to the AD.
While similar to using a Camaro clip in other applications there are some practical differences that matter. The dimensions of the Monte frame are NOT really similar to those of the AD truck frame. The Monte is much wider and you'll create some structure to match them up.
And of course you have the other issues associated with a clip project, mounting the fenders and grill and all.
