Yes, All informaiton above is good stuff to listen to. First thing is to see if the ribs are still hanging on. Even if they are, if the outside is rusty, you don't know what might be going on between the tubes. Might be best to have the ribs stripped and relayed to ensure all is sound.

And of course a chceking of the wall thickness would be in order. If the rust on the outside has caused a lot of pitting, you have to consider the amount og mateiral that will have to come off in getting that out.

B.Dudley