My concern regarding a car radio is the mounting of the aerial. The fewer holes in my Moggie the better
I too share your concern about drilling holes in otherwise perfectly good metalwork. One day I might pluck up courage to have a roof aerial fitted, which I think looks good for a start but also is the best place for radio reception.
In the meantime, when I fitted my radio last year (under the parcel shelf on the nearside!!) I opted for one of these:-
https://www.ebay.co.uk/itm/Retrosound-U ... 2749.l2649
Not the cheapest by any means - you can get them for well under a fiver, delivered from China! - but I didn't want to risk anything made out of cream cheese and chocolate

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I mounted it on the REAR window as there was plenty of cable to thread under the carpets and up behind the parcel shelf (which you may not get with a chocolate one!). It does require a live feed of course to power it up, which I did from a permanent live switched feed direct from the fuse box so that I can listen to the radio or cassette tape without the ignition having to be 'on'. Without the aerial being switch on the reception is just about audible but as soon as I flick the switch it becomes loud and crystal clear. On the move, reception can be a bit 'flaky' at times but overall I'm very satisfied with it.