I have heard of a 1930/31 Ruston 6AP which may well be coming onto the market - still in its original barn with a threshing mill and bruiser built by Bon Accord Engineering Co Ltd, Aberdeen.
The engine is said to have been in good working order last time used but has not been run for well over 10 years. It was well maintained while in use. It is in good condition and moves freely.
The drawback - its in Orkney.
If interested, I can pass you over to the vendor.