74 Dart drive shaft help

What you have posted 151.5cm is like 59.xx in. Usually shops want to measured from center of ujoint to tip of tail shaft or some even want you to buy a sip yoke and bottom it out in the trans and measure it center to center. That's actually going to make your done dimension shorter. The second way is the way we did it when I worked at a drive line shop.

Any way you look at it your going to want to go 1350 ujoints. One piece would be fine. If it's made from steel they probably are going to want to make it out of 3 1/2in tubing even though 3in .095 or even .083 should be just fine.