Heater Exchanger and CAC Corrosion on My TAMD63A-P Twins

Interesting maintenance issues.
Recently while servicing my CACs and exchangers I noticed some corrosion on 3 of the aluminum casings. The spacer rings had cracked by the drip holes. The o ring seats were destroyed.
I tried to have them repaired, but no one would touch it. I was told that because of the configuration of the casing, mounting on a milling machine was impossible.
Try as I might, I absolutely could not locate replacements, new or used.
I asked fellow boater for advice and was told to buy either Cats or Cumins! Umm, ok, that's not gonna work!
I used a Dremel and ground all of the corrosion away. A welding shop built up the area. Using a flat file and my Dremel, I reconstructed the seat. I had a machine shop make 4 spacer rings and the only unbroken one was going to be a spare.
The units are now working beautifully! WHEW! That was way too close for comfort!
A word to the wise, Stay on top of those aluminum exchangers! As a side note, I would love to talk to the designers that thought that aluminum was the way to go!

The twins were born in 1996 and have coming up on 1800 hours.