I assume your main sail is fastened to the boom by a boltrope. In these cases when one tacks hard over
and the boom swings the sail puts a center load on the boom bowing it in the middle.
If the main sheet is attached at the middle, just behind the vang, the boom will swing over and stop where the mainsheet is set but the clew of the sail will continue to travel bending the boom, sometimes permanitly.
If the mainsheet is attached at the end (clew) and the sail is stretched out or has a shelf, especially, it will put a center load on the boom when the sail fills.
I'm betting you have a mid boom mainsheet, the biggest culprit.
As for straightening the boom, if there are no external marks is could be straightend if done properly. But it will be weaker then it use to be. It has to be over bent the opposite way to get it straight again.
If you can find the manufacture it would probably be better to buy a new extrusion and keep your old end castings. There may be a sticker or making indicating the mfgr of the boom. Or even a Cal
site forum may know who made the standing rig for that year......................._/)