So I rebuilt my heater box a few years ago; the box had been busted by the previous owner, so I patched it with fiberglass and added a new foam seal kit. I also pressure tested the core, and it held pressure fine- until it didn't a couple days ago. Ordered a new core from Summit; got here in 2 days! Those guys are awesome. Just buttoned it up, with new heater hoses, took it for a test drive, and it's good as new. But this is not a job a 71 year old guy wants to do very often! It's nothing but heat pad/sunny deck/iPod/brewski time now. But knowing I was still able to fix that old Ranchero made me smile. Love these old cars.