LeRoi was not a common engine as all the cars listed for using it were rather obscure makes; Astra, Barbarino, Bartlett, Birch, Seneca and Steling (AMS-Sterling). There may be others as no list is complete!
You'd better check the engine again as it should be a V8 instead of 6..these are nice cars. A friend of mine restored one. Some parts can be difficult to get but in general parts are quite easy to find in Czech republic.