Here's an update on my use of an Astro van drive shaft when replacing the three speed with a T5 5 speed and the torque tube center cection with a '55-'62 center cection.

It works.

I moved my rear end back 1.5"

I used a 'swap adapter' from Hamilton intakes which moved the 5 speed back about 3/4"

The Astro van yoke was actually 1.5"-2" longer than the S10 yoke making the Astro shaft too long. I swaped the Astro yoke for the S10 yoke and the thing fit perfectly.

This worked for me. I make no guarantees. I hope this helps someone else.