500,
Those scuffs resemble a massive cold seizure but I am not positive since a cold seizure usually puts scuffs on the 4 corners of the piston. Intake side sezures are usually lubrication based. As Polar suggested it could be dirt, but in my experience dirt usually takes out the rod big end or the main bearings first (but not always). I wonder what oil the previous owner was running or if a tank got in that had no oil. I would attempt to hone the scuffs out by hand with 400 wet&dry with some WD40 as a lubricant. Clean it up best you can before judging whether you need a replate. If there are scratches or gouges under the scuffs then you will have no choice. I would suggest you look closely at the rod big end bearing for signs of grit or marks on the rollers (magnifying glass) and carefully roll the crank to feel if the main bearings are smooth. Hope this helps. Cam.
Seizure cause list:
heat (lack of cooling, air leaks, lean mixture)
lubrication (oil based)
contaminants (dirt, bad gas etc)
no warm up before WFO (stupid based)