Gravel kits installed obviously, but I bet they held their breath every time they went in and out of those strips!
Not at all.
Oh we had some fun back in the 80's playing with DCA, DOT or whatever flavour it was at the time.
I spent 10 years operating a C550 into and out of all kinds of surfaces, sealed, gravel, dirt and grass. The particular C550 had a FM amendment limiting the MTOW to 5700 kg. Yes, a gravel kit was a requirement that included a bleed air turbine to spin the nosewheel.
As I write this, I am looking at a photo of Ms Young landing the Joh Jet on a blacksoil strip at Malvern Hills near Blackall.