First of all the head is mounted in the wrong way, the milled slots in the middle of the head provide an airflow to cool the plug.

Then if it is the original head then it is a 359 and it is old.....
https://www.rctech.net/forum/onroad-...ssi-359-a.html
You can mount any Novarossi head or novarossi based like MAX, RB TOP, REX and some othe Nova based brands. But only normal heads, no low-cg heads.
You will face more problems with this engine, a P2 rod is used, that will be hard to find.....

My opinion is to invest not too much into this engine.