Thanks for the replies, guys. Especially the Gilbert manual pages. The photos I embedded are showing when I open the OGR S page on my computer, though. One photo was the power truck without any base plate, and the other was of a base plate with the coupler. But even on the page from the manual you sent, CW, they list a different part number for the bottom plate on the power unit than the other trucks. Three are listed, one for the power truck, one for a truck with no coupler and one with a truck with no coupler. So it LOOKS like there is some difference between the trucks with couplers. These locomotives really DON'T have an actual frame, but the individual trucks do. They're listed as "truck body assembly" The truck body assembly of the dummy trucks are a few thousandths wider than that of the power truck. The non power trucks have the bottom plate fitting inside the body assembly while the bottom plate will not fit inside the power truck's body assembly.
Since I had an "extra" non power truck bottom plate without a coupler, I decided to modify it. After grinding off a few tabs, and narrowing the plate on the ends, the plate now fits along the bottom of the body assembly, while the ends go between the body assembly sides. The tabs keep it in place. I used a small screw and nut to attach a cobbled coupler arm and coupler and now it's running on the layout for the first time in at least 30 years, perhaps a lot more while towing a few Pikemaster cars. With the thick plastic and hollow body, it magnifies the grinding noise similar to the Gilbert Baldwins. I guess it's the nature of the beast.
An Bill, the side frames I have didn't fit either since the small tabs were missing. I drilled and fit a piece of styrene rod, and the fit nicely and stay in place once the base plate is snapped in place. It makes sense that a power truck bottom plate should have a hole in it for lubrication. I guess I'll drill one. I'm stillmissing one side frame assembly, but Doug Peck has either metal or resin side frames available. So I guess I'll order one along with a few more restoration parts for myself and a few friends.
I picked up these AA units for a VERY cheap price, so if I have to invest a few more bucks, it's worth it. These things are WAY out of scale, but they're worth having just for their historic value alone. At least to my way of thinking.
And BTW, I embedded the original photos in this message. Let me know if they came through.