Bleeding master cylinder in the car

Agree 100%, when we got 67 in 2012, we made a mess with DOT 3 and it peeled firewall paint. DOT 5 went in next day and just bleed them until it pi$$ed purple. ZERO issues in 11 years. No compatibility issues here.
regarding getting brake fluid on your paint - I went to DOT 5 (silicone) in all my Darts and never looked back. It's expensive to buy but not as expensive as taking a bunch of stuff out to do a good job of repairing the mess when things go wrong. No need to get every little bit of DOT 3 out as the 2 fluids are compatible.