Just curious as to why MPC removed most portholes and other details from the F3's beyond that needed to aid in printing the sides? The details are already in the tools...so the cost savings had to be minimal at most. If costing more to remove the items. I think I read they had slips that fit into the tooling to alter the details.
As mentioned above, most of the nicer F-3 detail was already removed by the time MPC came onto the scene. They did remove the nose vents and made each side vent "removable" by changing out a set of slugs/inserts in the tool. Don't forget that you also have labor costs in addition to parts costs, and that combined is likely why most F-3 detail was removed in 1955 or so.
I am pretty sure the current PW F3 tooling is still original Lionel tooling from the PW era. They just refine and clean stuff up over time. Though I could be wrong...but at least they are new tools cast off the original master....but Im sure Lionel cast new working tools all the time in the 50's as well of a master.
It's still the original 1948 tool, although heavy modifications were made to it in 1955 -- enough to warrant changing the root of the part number from 2333 to 2367. I need to learn a bit more about how molds were made in the 1950's to say for certain, but the majority of the molds were likely not constructed with the use of a "master." Dimensional drawings exist for each and every part Lionel made, and skilled mold-makers transferred each detail from the drawing into the metal. The only likely use of a "master" would be for the complex curves of the nose. My guess is that they used a 2x or 4x model of the nose and then had everything pantographed into the steel.
Over time MPC removed the side vents as needed to allow for fancier decoration, along with the addition of the much-loathed ridges along the bottom edge of the die which helped in the printing og the stripes on the Santa Fe F-3.
By the late 70's the trend began a slow reversal, first bringing back the ports and nose grabs, then the two-piece ladders, then the screened vents, then the nose vents, then the side vents, and finally the elimination of the bottom ridges.
Jon 
I think it goes like this:
1979: The return of the portholes and nose grabs.
1991: The return of the two-piece horns (I think this is what you meant!), side vents and screened roof vents.
1998: The return of the nose vents.
1999: The elimination of the bottom ridges.
The changes went on unit there was just 1 vent, towards the rear of the body & ribs were put in on the lower part of the body ( similar as the Alcos). The B units did not have the ribs, but at some point lost the 2 vents on the side of the body & went to one. Lionel restored pretty much all of the original detail w/ the PWC F3 series although the Texas Special reissue B Unit only has one side vent. The only thing that has not been part back, IIRC, is the door detail on the nose, which was taken off when postwar Lionel made the 2242 New Haven F3s in 58
A funny thing about that missing side vent on the B-unit. It always bugged me, so one day I asked one of the tool room guys about it. He went right to a drawer on this workbench and handed me two small metal slugs..."You mean these?" Needless to say, all B-units from early 2001 forward have all the vents restored.
