You should be able to do a little Sherlock Holmes to figure out what is going on. That much oil is either (1) leaking, (2) being sucked into the ports and being burned or (3) Exxon is stealing oil from you at night.

Leaks are easy to spot at that high of a volume. Pour a quart of oil in one spot every 100 miles and you have a major mess....seems like you have eyeballed the thing....have you crawled underneath an looked up? Do so before you eliminate leaks.

Regarding #2, pull the plugs and look at them. If you are burning a quart per 100 miles, you should see some plug discoloration. One common leak on a small block Chevy occurs when people put RTV on their intake gaskets and the lower side slips down when the manifold is torqued. This leaves an open path from the valley into the intake port or ports. Sucks oil big time.

As for #3, if you see any guys in a tank truck hanging around your neighborhood.......