One post on the day he joined almost a year ago. The last activity on his account says he's never returned.
I don't doubt the Monte 3.9 will fit in the Impala. The Monte is pretty much a 2 door Impala with slightly different front bumpers and body lines for the 2 door chassis. Folks use the bolt-on Monte Carlo bumpers on the Impala for a slightly different look. The factory service manuals say they're for the Impala and the Monte-Carlo W-Body cars.
Darn nice of you to post this anyway. Maybe someone else can use the information.