Are parts between the same model of 3rd Generation S&W automatics interchangeable? What I mean is, could I take a new 4506 barrel or 1006 barrel advertised at Midwayusa.com and put it in my 4506 or 1006? If I waited the 90 days from S&W and received a new 1006 slide with fixed sight assembly, could I just put it on my 1006 to replace the existing slide with adjustable sights? I just would like to know if these pistols are made using interchangeable parts.

Most third generation guns have gone through several revisions, plus the changes with the TSW series. Barrel hood width is one that comes to mind, so no, not all parts will fall into place on all guns.

I see what you mean about the different revisions. What I'm especially interested in is a new barrel for my 1006 10mm. Midwayusa has the 1006 barrel for $105 in stock, and they show the 1006 R3 barrel as a separate part number and a special order item. What is the difference between the revisions? My 1006 is an older one I believe as the hammer and trigger are flash chromed.

I not sure but I would bet it's the barrel hood width. Sometimes getting the exact info from S&W is hard to do. The majority of customer service reps are just looking at a computer screen and have no idea what the actual differances are.

This is a bit dated, but to answer the OP, the R3 barrel from Midway does indeed have a wider barrel hood; the length may be a shade off as well, but does not take much to make it fit.