Sorry guys. I would have jumped in earlier but wife was on computer.
First, I'd like to again thank everyone for their two cents. I'm learning things I would have never even thought to ask. Keep it coming.
So here's my two cents:
As far as the DMV thing goes, Surf is somewhat right, but I don't think it would apply to me. As you can see on this
DMV: Composite Vehicles CT DMV page, there are provisions for what the State calls "composite vehicles". It does say that they are vehicles built with parts of more than one, which, technically I would be doing. However, it is aimed at vehicles that aren't yet registered. For example a home built hot rod or custom built whatever. Since mine is already registered and has a VIN and title assigned to it, I don't think this would apply. It is simply a repair, not the construction of a composite vehicle. I could be wrong, however, and I'm sure someone will interpret this differently.
To go with Harvey's idea, I, too, would have thought that making only one frame would have been the best way to go for Dodge cost wise. I guess not. Like Mike, where I live 2wds are urban legends-they exist somewhere, but I can't find anyone who's actually seen one. I bet the reverse is true for you guys down south. This is why I like this discussion. I would have never have known that they were that much different. Not that I don't have the technical ability to understand IFS vs my solid axle, just that it's an issue I would have never come across. So I guess Doug's frame is out. What do the 2wds have for springs up front? Are they a strut system or coil springs like my 4wd, but just located somewhere else?
Just as a side note, this
https://www.1stchryslerparts.com/oe_parts_catalog.html is a page from the online catalog of Westbury Dodge in Long Island. Fill in info at top for 2001 Dodge Ram 3500 then chose frame and frame assembly. It lists brand new frames for sale and there are separate listings for the 2wd and 4wd frames. There aren't part numbers there, just descriptions, but the prices of the two are slightly different, so I'd bet the they are not exactly the same. I guess that helps to answer that question.
Thanks anyway, Doug. Except for that, I would have jumped on it. I even Google mapped the trip out to you and it could have been done in a weekend. Oh well. Swing and a miss.
Anyone else know of 4wd frame available?