You need to find another "expert". The dual-range HydraMatic was one of the best-engineered automatic transmissions ever, but it takes someone familiar with it to make it work right. There are still plenty of repair parts available, and more than a few qualified technicians who can make it run right. For repair parts and references to someone able to work with you on it, try Fatsco Transmission Parts in New Jersey. They have a pretty good website so just Google the company name. It would be a real shame to scrap that unit on the advice of someone who probably wasn't even born when they were in production.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!