Suburban questions

[70GMCer]

Can I replace my 1970 leaf rear to a 1984 suburban leaf rear without any issues? Will everything be pretty much bolt up the same, except mine is a 12 bolt, and the burb is a 14 bolt, I think. Or, would the axles by themselves, be the same. Would the axles fit into the 12 bolt? Now that's assuming that I have the wider housing on mine. I'm thinking on changing to 5 bolt lug from 6 bolt, and if I can use the burb parts, I will. Next, can the gas tank from the burb fit between the frame in the back, like the blazers tanks do?

thanks, steve