You already have the tooling, in the main. You have offered the L2a Mohawk (I have it), and this is an L2d with a sunken Elesco FWH. There are no doubt other detail differences, and I have not sat down and inspected both the L2a and L2d engines and tenders, but this has to be a promising place to start, relative to the tooling. Only the boiler detailing should need any changes, I would think.
But, besides being a tasty Mohawk, and who doesn't need more of those?, the main reason I have picked this loco to request, is that, unlike all the Hudsons and all the Niagaras and all the big NYC Pacifics and Mikados, this thing actually still exists!
From the 2018 NYCSHS calendar:
(We'll discuss the real L3a 3001 in Indiana at a later date, speaking of tooling you already have that needs change.)