I fixed that Tedford valve !! it still leaks , I just instaled a new ( $ 22 ) valve on the end of the 3 " ABS pipe on the outside !! It took about 1 hour !! The Tedford valve rebuild kits are $30 each so I saved $40 ! I know its not stock but it works !! Look at pixs .
I purchased a '72 Ambassador for my Parent to camp with us and I'm in the process of customizing it for their taste. I've replaced the toilet but the black tank valve was leaking pretty bad. I came to this site to find out how to access it but I believe I'll copy this idea and put a new valve at the connection! Great forum already on my first day!.