You should only deal with smog reading all systems, "green" vs a "red" being a fault or a Check Engine Light fail.
No computer hookup with older OB1 vehicles instead requiring the visual, carbon vacuum line disconnect checking the evap system as well gas cap for function. Only then the tailpipe sniff test.
With coolant acting like oil on the cats, both turning into carbon coating the ceramic honeycomb material inside the cats also increasing backpressure as well the rare earth ($$$) metals reducing the ability of converter to do it's thing hence high HC numbers and a fail over the set maximum allowed the vehicle.
Depending on how long time wise and mileage driven on a sick engine can mean the cats are dead, part dead or still able to function if lugky or washed and rescued.
I spent 22 years hanging out and helping at a friends muffler shop wiyh failed cats the most money made replacing them here in **** Kalif. being the worse or matching one other state in the country with strict smog checks.
I own a Sun Investigator machine half the size of a Smart car a full on beast before going in for smog smog checks or tuneups after engine modifications plus friends vehicles.
Also a Hunter four wheel alignment machine used once checked the LR having solid axles with zero alignment issues 143K miles later and counting.
Your lucky if replacement cats are required being in one of the 48 or 49 state replacements. Only a couple manufactures sell legally in Kalif. being stupid expensive the rest said screw Kalif. and pulled out.
Example, OB1 vehicles now required to install more expensive and flow restrictive OB2 cats on older OB1 vehicles.
MagnaFlow sells 48/49 state OB1 cats but will not ship to a Kalif. mailing address. Must use a out of Kalif. friends address then ship to me.
Save and reinstall the old cat stainless heat shields having dates stamped before that new POS law went into effect. Those 48/49 state cats pass Kalif. smog super clean with the sniff test even with a performance chip installed. Talking $87 each cat when I stocked up four cats five years ago. Present MagnaFlows installed 19 years ago at 117K miles service still operating like new smog numbers.
Sorry I ran off on your thread.
One suggestion sounds goofy, I used "Cab Soap" a super strong cleaning powder used on big rigs, a cup of powder to two gallons of hot water sloshing spoiled converters then a good rinse. Set near heat lamps vertically overnight, next day reinstalled they functioned again.
This works best with cats that have flanges welded into at each end.
Cats worth a try to rescue vs looking at $800-$1,100 plus replacements.
Don't laugh, it has saved a few friends owning and street racing BMW's after messing up cats due to turbo boost lifting heads and by anti freeze "spoiling" plus after a few engines that auto disassembled at 8,400 rpm's ending up with cats swallowing a lot of oil.
Note both anti-freeze and oil soaked cats were not driven any distance at all being gearheads knowing driving any distance destroys cats.
I did head replacements on a friends "Must Have" 5.0 LR found dead and like yours cheap for a reason. We were up and running between $1,100-$1,300 including purchase price. My free labor as usual, paid later in fish and Bier. A never again touching a 5.0 engine.
It's now used to launch his 24' sport fishing boat in salt water down the ramp ending with the top of the rear tyres submerged in saltwater the stopping depth to launch. Drain holes added with holesaw into the floorboards for draining out the interior
Good hunting and rescue with your project.
My friends have shops with lifts plus the space with over 3/4 mentioning part it out then buy one that runs and not so bad off being money ahead as the unknowns can get costly rescuing.....~~=o&o>......