Mif the cats themselves are fine I'd just repair the rest of the system. Removing them will make for less fab work but its kind of ghetto IMO, especially if they are fine. Will it run without them, yes. Will it cause problems, maybe. Is the right way to repair anything, never.

 

Here you go JJ.

Amazon.com: 1994 1995 Land Rover Discovery Exhaust System Cat Back Muffler Pipe: Automotive

Parts Bin - Auto Parts and Accessories Catalog - w0133-1651420 1995 land_rover discovery catalytic_converter bosal - 1995 Discovery Bosal

Another option is to go to the local muffler shop and have them delete the cats and run a whole new exhaust from the manifolds back, they get to keep the cats.
All you need is the center muffler, thats $100 installed, then they run the rest of the pipe, not a big deal, they bend it themselves.
Go in to Muffler Man or some other hole in the wall place and tell them you want a custom exhaust, should be under $500 out the door, especially if you tell them you are paying in cash and you do not need a receipt or warranty.

Rust like this is what happens when cars sit for a year in MI under a tree.

 

In PA, pre 1996 is exempt, 96 and later are required to pass emissions.