Thanks for all the tips, gang. Yes, there was indeed a leak as I drained ~6 quarts from the crankcase. It wasn't clear where the failure was and I didn't spend a whole lot of time looking for it. Put on the new plenum, lower gasket set and coolant elbows. Cleaned the throttle body well (very carboned up) and put it back together. Ran great but still had a small coolant leak from the front of the motor. Upon closer inspection, I noticed the water pump has two weep holes- one looking up at about a 45 degree angle and one down below, well hidden. The hidden one was leaking so off to Auto-Zone I go and after a few more bruised knuckles, she seems to hold her fluids now. All said, I got to learn a great deal about this car and spent some quality time in the garage (heated and well stocked beer fridge) between this and both daughters cars. What a way to spend a Thanksgiving- hope all you had a good holiday!