Replacing the head on a glow engine allows you to burn model diesel fuel instead of glow fuel; but unfortunately you do not obtain all the benefits of a diesel engine. There are a number of other differences -particularly with carburation. There is also a risk - diesels run at double the compression ratio of glow engines and so there is considerable extra stain on the engine, especially on the crank pin. A number have been known to fail. Why risk a good engine for questionable results?
Diesels are great, (I have several), buy an engine designed for that purpose.
Model diesel fuel is not the same stuff as at a gas station; but a mixture of kerosene,oil and ether. plus a little 'ignition improver' additive