ok to use unleaded gas in 1960 volvo 544? which octane to use

A 1960 model will likely not have hardened valve seats. Unleaded fuel is really hard on the old style valve seats. I would either have it converted or run a lead substitute with the fuel.

thanks. i thought so. have any idea which octane i should use?

Unknown, but I would think just plain old regular unleaded available in your area would be the best place to start. If you hear any pinging step up to premium.