You need to be able to flex your suspension from full stuff to full droop. Measure yoke to yoke in both positions and that tells you want your driveshaft lengths need to be.
At full droop you need to use a protractor to see what angle your driveshaft is at. That will tell you if you need single or double cardan joints.
GLFWDA member since 1979.
Member Southern Michigan Rock Crawlers.