No one armed with just your age can say what you can do safely. I have a 32 inch Husqvarna and will be 75 on my birthday. It is a handful to start but not that tough so as to avoid using it. I do find I don't last very long working with the saw up over my head.
Some vendors of chain saws, especially if they repair saws, will have a "test" log on which they will probably let you make some test cuts if you convince them you are a serious buyer and just need to "size" yourself to the right saw.
Patrick