So, in our little world of make-believe, why don't you create a PRR 4-8-4...you know, something like an S-2 boiler (and tender) on, say, on an ATSF class 3776 chassis?
Why not?
What-if's are fun in their own genre...IMHO, of course.
Imagine the workbench mayhem as you morph two fine engines into a new unique behemoth..