There is a change in the classic car market. Based on a fear of not being able to run with modern traffic.
My MG ZA Magnette is very much original spec. But even as an owner for 41 years I am considering upgrades I didn't want to do years ago.
But the popular approach for the Magnette, and its sports car sister the MGA, is to drop in a larger engine from a related model going from 1500 to typically 1800 (MGB based, and readily available). Modifications of this sort remain unobtrusive. Some go as far as 2 litre twin cams or V8s, but this poses problems in certain countries like France, or anywhere that road registration rules limit the scope of change.
A related bigger bore 4 cyclinder doesn't affect the looks and does give a more sprightly vehicle, and when coupled with a suitable gearbox and rear axle ratio can make the car more pleasurable at the apparently 'obligatory' 70mph (110kmph) cruise speed. A car with mechanical mods used to have a lower value than an original car, now people steer clear of original spec cars!
Running boards tend to be fitted to earlier cars, mostly pre-WW2 that not only don't cruise at 70, they don't stop that well either, and donor upgrade parts are not really available. Your modern owner is a bit wary of all of this. And unlike a bike, it cannot be considered a suitable ornament for the house! They take up a lot of space.