Building Tudor/rolex

[Aiivinchy]

I recently got into servicing mechanical and automatic watches. So far I’ve done full disassembly’s; ultrasonic clean, oil, and reassemble to a few ETA movements and I’m itching for a vintage Rolex now. My question is, I’m currently looking at a full mechanical 1940 tudor movement with dial/hands and wondering if I can use a 6565 case or a 6580 case for it? I believe the dial is 28mm, or is it frowned upon to get a mechanical hand wind 1600 Cellini and modify it to fit an oyster case as well?

[watchmaker]

Frowned upon by whom?

You can do anything you like with things you own. But it will obviously not be considered a genuine product.