I haven't tried mixing and matching cages, but have run into difficulties reinstalling cages when I may not have taken them off the right way. I'd tread lightly.

In addition to the Shimano long-cages that have been sugggested there's the Campy Racing T, not too dear used and designed to accommodate their 53/42/30 chainset combined with their 13-29 cassettes. There was an 8/9-speed version that I have used as an excellent friction derailleur. It has enough lateral range to easily accommodate the wide cassette of a 130 mm hub. You may need to try different shift levers. There's a real difference in how much cable they pull, and the sprockets are pretty closely packed together. You don't want the lever travel to be too sensitive - modern cogsets grab and release the chain quite readily if you don't have it feathered just right.