Oddly enough I bought a lid/brick from a person that removed it from his car a year ago.
It was fine on his vehicle, so I installed without pressure testing it.
After on the vehicle, something told me to check it, before adding water so I plugged 1 port with my thump & blew in the other.
I quickly felt the pressure drop. It is an internal leak in the core with no visible damage.
The leak is bad enough that it would have quickly done engine damage.
All we can figure is there was a speck of something corrosive in there that acted on the aluminum over time.
It is typically about $40-$50 for the plates & $100 +/- for the welding labor.
At this point, if the factory bricks are hard to come by or possibly going into obsolescence, I figured why not start with new while I can still get one
To buy a used one, then spend $150 modifying it to potentially have it go bad didn't seem like a good deal.
The Aftermarket units are $12-1400, so not appealing either.