I remember when..............
Flying was an exciting event,...but the other flight(s) were likely to be on a prop plane.
I flew on a 4 engine prop recip (not turbo) aircraft down around Atlanta in 69.
The FIRST thing you notice approaching the thing is that OIL is leaking FROM EVERYWHERE. This does not bring a note of confidence to the procedure.
Then you sit down, and happen to get a window seat RIGHT were if one of the blades left the scene, it would head straight for YOU
So you watch the thing crank up, and the cooling flaps are open on the cowl, and you can see the engine down in there. The damn thing looks like a badly loaded Maytag!!! It moves, jumps, jerks, coughs, sputters and looks like it's gonna come right off the wing!!!!
And you guys worry about whether your 318/ 360 swap vibrates. I doubt that any recip pilot ever worried about such trivial matters.