Your torque tube housing is mounted to the springs with a hinge. This hinge will have to be immobilized (welded) if you use a later third member and an open driveline.

Just what do you expect to gain from converting to open driveline? Your ratio is 4.11. any 3rd member that will bolt in is a 3.90. You seem to be wanting to change it just to change it. There is nothing wrong with the design of it. If you are after higher gears, there are ring and pinion kits that will accomplish that. You seem to be wanting to go to a lot of trouble to accomplish nothing but the change to an open driveline.

The reason I went to open driveline in my '54 was to install an overdrive. That will give me an advantage in gearing. For you to change from a 4.11 rear to a 3.90 just to get an open driveline is a lot of work for little advantage.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.