Yes earlier (and larger) M&S engines do still exist, and are operable....

The three cylinder version of the 17.5 inch bore M&S engine is pretty rare and had been dropped from the product line by the mid-1930s. The web page identifies the original installation of this engine as being in Le Sueur, MN. There were also several of these three cylinder engines used in the municipal power plant at Siloam Springs, Arkansas.

http://www.youtube.com/watch?v=d9Z2rebTRwo

And here is a link to a web page showing the engine, they also have a restored Fairbanks-Morse.

http://www.pioneerpowershow.com/diesel.html

You can see from the description how much work it takes to set up a big Diesel engine properly so that you can run it in a building. It is usually a lot easier to use an operable locomotive for demonstrations, particularly since switchers and roadswitchers with full handrails provide a good speaking platform to present interpretive lectures.

There are a number of outdated 1920s and 1930s Diesel engines sitting decommissioned but intact in some very large buildings. New York and Boston have a bunch of them, but they are on private property and visitors are not welcome so there is no point in posting them on a public forum. Most such engines are in buildings that will eventually be taken down by demolition so the only way they are ever going anyplace is as scrap along with the steel structure of the building. The services the large Diesels provided are now usually handled by much smaller housed units outdoors at ground level or in underground vaults beneath parking lots. Architects now recognize that trapping an engine permanently in a building is not a very good idea.

PC