You will have an idea from driving it in stock condition at 55 mph. Certainly loud enough to cause hearing damage with prolonged exposure.What makes them so loud? If you put a mild tire on them and a mild exhaust with a modern engine, some dynamat on the firewall and floors it shouldn’t be any worse than any other truck of this vintage right? How loud is loud as hell?
Yeah, I suppose all those upgrades will make a significant improvement in this regard. I haven't had the pleasure of driving a resto mod 55. There are a few videos available online and it's difficult to tell from them. Still loud by modern standards seems to me.