I'd clean it up as suggested above, getting all the lead scrubbed out with a product just for that ... don't forget to let it soak as directed.
If the crown is messed up there are methods for you to clean up the crown at home yourself using a drill and a brass machine bolt with a round head and a standard screw driver cut. Using the brass components it's hard to injure your barrel, .. but that is always a possibility...A smith could probably clean it up for real cheap or you could have him cut a completely new crown ... considering the age of the rifle and it's relative value I'd just try everything else before I messed with the crown.
I'd also pop it out of the stock if you haven't already, and reassemble it with firm even pressure looking to see if the stock is impacting the barrel in any significant way.
Now please don't get offended here with my next point, as it is meant for those that may have forgotten, ... but there are a lot of folks that do forget the simple rule of adjusting rear sights in the same direction of where you wish the bullets to go... so if you're currently hitting low left and the rear sight is adjustable for both windage and elevation you'd want to move your REAR sight up and to the right to move your shots up and to the right. Please forgive me if this sounds silly, but even though you may be solid on this, lots of new shooters don't know and some experienced shooters forget.
Good luck in getting the old JC Higgins spitting where your looking.