Oil furnace converted to natural gas

First time I ever saw this before. An oil burning furnace converted to use natural gas. Never knew it was even possible.
Question is, has anyone ever seen this before?

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It’s called a gas gun conversion. I had one done about 20 years ago.

Not only saw it–I have converted quite a bunch over the years (70’s-80’s). Very common then.

Yep…I see a few of them here and there. Oldies but hardly any issues.

Quiet too.

Just a question: (I know they are quite safe and have lasted)

Would an AHJ allow these conversions today if not dually certified as newer Weil-McLean and Teledyne units have been?