Webra 61 Black head will also be an alternative if you want an engine fromthat time frame. I have such engine myself (NIB) that I plan to mount in a Marabu (Bruno Giezendanner WC model 1969, 1971 - he used such engine in his plane). But a new modern more reliable 2-stroke like OS 55AX or Evolution .60 NX should be fine also.

/Bo