No experience but here is someone who has.
https://sp9010.ncry.org/models.htmFrom the website:
On the Don Pardo shell
Diecast Models: Del Prado
Del Prado is a Spanish collectibles company founded in 1988 in Madrid. They offer a collectible set of "The World's Great Locomotives" in N scale (1:160), sold by online subscription. Included in the set is a representation of the Krauss-Maffei ML 4000 C'C' Denver & Rio Grande USA Prototype. The models appeared in 2005.
It appears from the front 3/4 view that the mold makers may not have had the benefit of anything but a side view drawing. (We'll leave it at that.)
The set may still be available from Del Prado, and single units of the KM model often appear in online auctions at modest prices.
http://www.delpradocollections.com/us/group.asp?CollectionID=1From the same web page. Mike Danneman built a shell had a friend cast it and used a Kato SD45 mechanism.
Scratchbuilt Models: N Scale
Mike Danneman scratchbuilt these three fantastic Krauss-Maffei ML 4000 C'C' Prototypes. Here's his account:
"I model N scale Rio Grande, and I always thought it would be neat to have a KM for the layout. After checking plans and other sources, I realized that I'd have to scratchbuild a body shell that would hopefully work over a modified mechanism. I choose the N scale Kato SD45 mechanism since its length is only a few inches different than the KM. I built my original KM shell out of styrene, with only a few commercial parts added. The lower portion of the nose and pilot are from a Kato F7 shell, and the cowl and cab is made of .015 styrene. The fuel tank and trucks are modified Kato parts, used to retain the reliability of a good-running model."
After finishing the first model, I dreaded trying to build two more. Neighbor Keith Sorci, who casts 1/24 and 1/25 scale automobiles, saved the day and cast three KM shells for me using my model as a master. Because I didn't construct the master with casting shells in resin in mind, I was only able to get a a few resin shells out of the mold. The cast resin models were then finished in Rio Grande paint and sent out onto my Rio Grande Moffat Road for testing (with Dynamometer car No. 10 tagging along, of course). The models aren't perfect, but as far as I know, they are the only N scale ML 4000 (Prototypes) out there!"
For more information on how Mike built the models, please see the November-December 2003 "N Scale Railroading" magazine.