I think they just faded away. There is a lot of machining involved in the conversion and they were costly. I have seen them on model A's and a friend had a 46 Ford ragtop with one of these conversions. They probably used a BW OD which started out as an open driveline unit. It would cost more to do this type of conversion than to convert to an open driveline and use a later OD trans or an automatic/OD. Tom's book was printed in 1991 but I had seen a similar article many years earlier. Gearvendors makes a good unit which is used on a variety of manual & auto transmissions but I'm not aware that they do torque tube conversions.
Fred

1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine