Just a cautionary note about screwdrivers. Saw the reference to the "Phillips" screws. Once had a lot of Phillips screw drivers from the old Sears. They all came to a sharp point, and were engraved with the Phillips patent numbers (or patent pending?) But I had to blunt all the points to get a tight fit, because I never saw a Phillips? screwhead that didn't have a flat area at the bottom of the recess. Finally got a copy of "Machinery's Handbook." Had the Phillips standard recess drawn up. It is flat-bottomed.
Still, there are other similar screws where the fit is not too good still. Turned to the internet. Aha! The generic name for such screw heads is "cross-recessed" or some such. Point is, when I looked further, there were 3 different (each with its own patent, I presume) systems of such screws... at that time. Who knows, more now? (I know wood deck screws have gone mad with which screw and driver have the better grip-- each box comes with a pair of its drivers.) Sadly, I have lost my bookmark, but it's out there.
As for screw drivers, I'd avoid the pretty ones with chrome plating. Chrome is very hard, and makes a hard surface for poor steel, and slippery. Rust-proofs it too, until it deforms under hard work and flakes off. Try to find some alloy steel drivers, unplated. Baltimore Tool used to make some real tools. Hope they are still in business-- found their stuff at hardware stores that catered to farmers. not city slickers.
Lionel diagrams used to refer to "posidrive" screws... or was it "pozidrive"? Don't know if that was one of the three systems I found (for machine screws). The Handbook used generic descriptions: Class 1, 2, or 3. Well, on Federal jobs you must avoid the dread "proprietary" by name spec.
I did note with interest that in the picture above, the 4 slots have parallel sides. Other classes have sides that taper inward as you go out. Some slots get narrower as you go down. Others do both. Or neither. And then there is the dreaded conic angle. Back when, the English liked different conic angles than the Americans, so there are two choices... Did you know that metric standards for dimensions are actually managed here in the US by our technical associations, for the entire world? Yes, headquartered right here in sight of the Capitol dome, like any good lobbyist. In the land of the last people to use inches.
In some late US Lionel production, with the picture layout of parts schematic and parts description list, the screws are dimensioned in US conventional units (inches, ca 1954 Unified standard), but in a used example ("2380" road number series, late 90's... '97 for sure, poss '96 & later... 00?) just obtained, the screws associated with the then new TMCC items in GP-7&9s the screws actually are the closest metric matches, the self-tapping ones, anyway. A tip... I think the self-tapping (metric?) screws driven into the 4 plastic post corners of the shell are oversized for the holes in these posts, leading to splitting. You can't get a TCA 10 if you change these screws to what they should have been when replacing a split rear post, of course. Maybe posidrive screws were only ever metric, like the E-circlips which were invented late, and only have metric sizes, altho typically used on 3/16" motor shafts. So much to forget... .
In any case, you need a matching screw driver, of the correct size in the series, to avoid the dread single point contact while twisting the driver with a pipe wrench. Get them with square shanks. You will also need the heated version, I see. These are made of that special alloy, "unobtainium."
--Frank