I swapped my TH350 with a 200-4R in my 1970 GS 350. Even though the transmission body is the exact same length. My drive shaft only has 1/2 an inch before it bottoms out in the tranny tail-shaft. I also replaced the rear stock upper and lower trailing arms with after market tubular components. The uppers are adjustable and I think that is where I lost the space between the tail-shaft and pinion yoke. I failed to note how much space the front (splined end) of the drive shaft had prior to dis-assembly but a 1/2 inch certainly seems to be shy of what is needed to safely telescope in and out of the tranny tail-shaft. Does anyone know what a safe measurement would be?
I have about an inch on my 2004r. A drive shaft builder should be able to mill a 1/2 inch off the yoke. They did that for my yoke.
I have no idea if the turbo400 vs turbo350 350 vs 455 has any bearing on it but my 70 455 car had a turbo400. I swapped for a turbo200-4R, 8.5 10-bolt and used a stock '71 turbo 350 drive shaft and it fit perfectly. About 1 1/8" sticking out of the back of the seal.