There is a response to a reader’s enquiry in ME Vol. 131 (1965) page 191 as follows:
You do not say whether you prefer a petrol or a steam plant or at what scale you propose to build Moorcock. A 5-10cc petrol engine will drive a 1/4in scale model and a suitable steam plant is The Trojan M6 in the Plans Catalogue or the Stuart 10V.
For the larger scale model you could use a 15-30cc petrol engine, the Warrior steam engine (M7) or the Stuart Double 10V.