replacement engine for a cletrac R or H

[phil burandt]

Hi,
I have found 2 cletrac bulldozers.  One is a R and doesn't have the right engine in it. I would like to find the Buda engine that goes in it. The other is a H and has no engine.  It should have a Weidley engine.  How hard would it be to find an engine for either  one of these and what serial numbers would I  be looking for? Any ideas, leads or information would be appreciated.
Thanks
Phil