Tale of Two Wastelands, the mod that lets you play Fallout 3 and its DLC in Fallout: New Vegas, and travel between the two worlds with the same character, has received its long-awaited 3.2 update—a "total rebuild" that has been in the works for more than three years.
The mod will let you play through Fallout 3 and Fallout: New Vegas with the same character, and you can switch between DC and the Mojave Wasteland by visiting train stations. It's a total conversion mod that sees all of Fallout 3's quests and settings transplanted into Fallout: New Vegas's engine, complete with mechanics that you remember from New Vegas like weapon mods and the companion wheel.
The 3.2 update has been in the works since 2015, and its changelog is more than 30,000 lines long (the whole thing is in this Reddit thread, if you're keen). It's described as a "total rebuild" of the mod on its FAQ page, so if you were ever curious about playing it, now is the time to try it out.
You'll need clean installs of both games along with all DLC to run it, and it should work with both Steam and GOG versions. You can download it on this page, where you'll also find full instructions on how to get it running.
It can cause havoc with other mods, so don't expect your Fallout 3 or New Vegas mods to work automatically with it. However, many mods will have separate versions specifically for Tale of Two Wastelands—its forums have a page dedicated to telling you which mods are compatible and how to get them working. And again, check out the FAQ before deciding whether or not to jump in.
Thanks, DSO Gaming.