Forgot to add: the head from an OS FT-120 will not fit (I'm 99% sure).

Just look at the position of the exhaust and intake pipes relative to the pushrod tubes: if you tried to place such a cylinder head on your radial, the intake and exhaust pipes woud be facing forward (more or less), while on the radial the intake is in the back of the head and the exhaust is in the rear right corner.

On the other hand the FS-61 head should fit.

Finally, the Graupner website lists its prices INCLUDING VAT. Orders toward the US should not include this tax, so, if you decide to buy from Graupner, you should pay a price close to 70€, not the 87€ listed. This price, obviously, does not include shipping costs.

Radial.