Williams "J" trailing truck

You probably know, of course, the WBB ATSF Blue Goose is not a model of the actual Blue Goose - that was a Santa Fe 3460-class 4-6-4 (the ATSF did not call them "Hudsons", I believe), and the WBB "model" is actually an interpretaion of the N&W streamlined 4-8-4.  The 2 loco types do favor, a bit. So, you can only make it so accurate.

However, that should never stop anyone who's determined. I have turned a 4-6-2 into a 4-6-4 - Lionel's nice but too-long (it's literally just that: too long in the firebox for the Erie/USRA Heavy pacific prototype) Pacific makes a very convincing Hudson.

In your case, go to the Lionel website and go to "Replacement Parts" (it's under "Support"); do a few searches on locos with likely trailing trucks. You can order it easily from the website; takes about a week to get it - I order parts from them all the time. You'll have to fiddle to get it mounted.

Try it. I highly recommend modifying the new truck for a fit, rather than your locomotive.

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My ex-Pacific Hudson (bear in mind this is a full-scale model); not-quite-finished project, as usual, of course. (A Burlington fan could make this a convincing CB&Q Hudson, with the right tender.):

Also, the Williams J (a reproduction of the Lionel postwar J) is a traditional-sized locomotive, not scale. I have one, too. It's a true beauty. But it is much shorter than my MTH Premier J, and the trailing truck area is one of the places Lionel and Williams compressed the model to make it run on tighter curves.

Still, I get what you're thinking. It would be interesting to see what it looks like with a longer truck. But I don't know of anyone who has made such a conversion. So why not become the first?