Put sheets of newspaper under it when it's parked to see if its really leaking, and maybe from where.
When new, those 216 engines did normally use about 1 quart per 1000 miles, so honestly --- it also took a long time to break those rings in , and 1 quart per 300 miles wasn't unusual for breakin-in.
If you can't find the leak, and it runs OK, I would live with the quart of oil when needed. Cheaper than a rebuild. But check your compression just to be sure.
