I installed a new LH running board and brackets on my 49 this winter, the originals had been long removed by a previous owner as a result of a fender bender and the parts were lost by the time I got the truck.
I immediately noticed that the new brackets did NOT align the running board correctly and it sat low, not unlike what I see there. Shimming was necessary, so if someone has replaced the brackets at some point that could be what you're looking at.
In particular I notice that the running board looks like it is sitting below the rear fender, which leads me to think that could be the issue?