how do I know where to drill and mount rear fenders on these? It looks like they don't have the pre drilled holes...

1953-1956 Ford F100 1/2 Ton Bedsides

 

In reality, where ever you want. Mount them up higher and slam your truck, keep your truck stock height and lower the fenders for that slammed in the weeds look. But if you want stock location make a cardboard template off your existing bed sides or use somebody elses sides if you don't have any to make the template.

 

Keep in mind if you mount the fenders higher or lower you will have issues where the fenders bolt to the running boards.

 

Does this help? These are the measurements for the bottom bolts on a '53 bedside.

 

We'll I have a bed right now, but it came off a 57. I didn't buy it, it came with the truck when I bought it. It's in pretty good shape, but the fenders are 3 inches too high. I thought about practicing on it and trying to lower fenders, and patch old fender bolt holes, but I'll probably warp the panels. I have it on Craigslist, but it's looking like the best I can get is around $275.

 

Mount the running boards. Than mount the fenders to them.
Now line the fenders and boards up to where they look and
function the best and nail them in.