I've seen a site a while (meaning years years) ago from someone who swapped a LS4 into a 2000-ish Monte Carlo. I can't find it any more, but from what I remember there was a lot of fabrication involved to get it to fit (e.g. I believe I remember the radiator support had to be moved forward about 2"). So it is possible, but the benefits don't justify the cost unless you really value being different.