attaching '74 rear frame to '69 frame???

[doowoppwer]

i have a '69 c20 with coil springs in the rear. I have access to the back half of a '74 c20 with leaf springs. the '74 frame web is 8" and the '69 is 6". looking for advice. should I cut my back half off and graft the '74 to my frame? should I remove all the leaf spring stuff and attach it to my frame? should I head in a different direction?
thanks in advance for any input.

I failed to mention that not only do I want the leaf springs, I also want the axle.