Seems like a grinder on the bottom caliper ”ear” would take care of it
Imho, don't; the problem isn't the caliper but the fender.
The fender's mounting holes to the brace between the sliders are too far towards the rear/bottom of the fender. So, when the fender's mounted on the brace, the rear/bottom of the fender, and the "fender support", are too high - the "fender support" on my bike passes well clear of the bottom of the Lockheed calipers with exactly the same "ear".
suspect this is a cheap knock-off of the cheap knock-off (Girling) of the original AP
Don't know of any only ones I know of are Grimeca and Wassell Girling - and afaik the latter have "GIRLING" cast on?
Just as a matter of interest, have you checked the dimensions of parts - mounting holes ID, hose/pipe threads, pistons ID? Reason I ask is I was wondering it might be a Grimeca? Years ago, somehow Grimeca were allowed to pattern the Lockheed caliper but 'metricate' it - mounting holes are 10 mm instead of 3/8", threads are M10x1.0 instead of 3/8"-24, piston OD is 41 mm. instead of 1-5/8". The current Grimecas look quite different but iirc the originals were very similar to the Lockheeds.