I can put a bit of a spin on this, since I just did mine a few weeks ago. Mine is an '84, and it has the optional gas heater, which makes things a bit more complicated. I guess without the gas heater, the cross over tube can be put in place BEFORE reinstalling the tank? With the gas heater, the duct from the heater passes between the cross over tube and the tank. I didn't pay attention to how the tube was routed when I dropped the tank, and although I had a general idea of how it was located, I found on reinstalling the tank that being just slightly off makes a difference. I had to put the cross over tube in place, then put the tank in place, then reach in from the sides and find the tube and push it into the grommet(s) on top of the tank. This is in addition to fishing the vent lines out the sides too. It took 6 tries to get it just right-by myself-and even though I knew a floor jack would have helped (I have two) I kept thinking "this will be the last time". Not a fun job, and ho
pefully one that won't have to be done again for another 24 years. One other thing-if you are dropping the tank and have the gas heater, use the opportunity to disconnect the ductwork to the heater and vacuum it out with a shop vac. My gas heater didn't work at the time, but it does now, and I have no idea how long it had not been working. When I did get it to fire up, I got some funky odors from it for a while, and I did find that I had a mouse living in there somewhere, as I blew him and his nest out the second time I turned the heater on. Luckily, the smell is now gone.
 Jeff