Vintage PC Frame - Where Do I start

I've been looking into building a PC in a Vintage frame. I love the exterior, but I understand alot of the back (and likely the interior) metal will need to be replaced...

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I was wondering if anyone else has done this? If so, where how do I start? - I'm thinking taking dimensions of the build, maybe doing a 3D print of it? or going to a fabricator bending the metal according to dimensions.

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Thanks,