2 qts is a lot of oil. Could be a head gasket, but that big of a leak it ought to run like do-do. You say the block is from the 90's. Has it been run before? Is there water in the oil pan? If not then oil pressure is pushing it into the coolant. The suggestion to used air to test the block sounds good. That is really a bummer. Pull the plugs and look for signs of water in the cylinder that would be a pretty good indication of a head gasket, but not a 100% check.