I learn something new every day...when I feel like it! I talked with Brian (see this month's gallery) and he referred me to a couple of resources for a third member from a '68 to '72 3/4 ton auto trans truck. In turn I was sent to this website
http://67-72chevytrucks.com/ where I registered and looked in "'67 to '72 parts for sale". (that was before the above reply and you were right Dan!) Found a guy in Arizona with a couple of rear ends that will work for my application with 4:10 gears. Says he will sell for $175 plus shipping. To be continued...