You'd be surprised (or maybe not) at the amount of people asking forums for opinions and the first thing they're concerned with is resale. I guess nobody wants to ruin their cars for the future.
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I just did the sacrilegious thing of cutting the dash in my 65 Mustang to install a modern stereo with bluetooth phone connection etc. It's been my daily driver for the past 3 months, so I wanted easy access to the stereo, rather than having it tucked away in the glovebox. Some people think it's the worst thing to do to a car ever. I'm enjoying it much more now as it's so much easier to control my music. It's not a rare model, so it doesn't matter.
Likewise with my vette. It's a 73 with 80's front end and 80's interior, aftermarket suspension arms, a 400 sbc and soon to have a TKO slapped in to replace the auto. My car, my choice. Sure if I ever sell it (not likely) there may be a few people who won't buy it because it's modified, but there are other people that would be interested as it has been upgraded. Wabco and Dirty Rat both have cars that are not stock and are awesome.
Build your cars for you!