cam lobe wear and piston scuff pics

[gradon]

I made the same mistake above--thinking they were the stroker pistons--which was why I was questioning the bore clearance. So there was an issue of what happened to the stock pistons in the 4.0 and what happened to the re-used cam in the stroker.

[Heck]

If those are the stock pistons out of a '03 (like yours and mine), that is extreme wear for 40,000 miles. And '03's came with a coated skirt from the factory, yours is just scrubbed off. The pistons were also hypereutectic for a tighter bore clearance and better emissions.
I pulled my engine apart the first time at ~80,000. My pistons didn't have half that much wear, barely through the coating but no wear on the metal. My cam looked nearly as bad, and my stock springs tested at less than 40# seated (should have been about twice that). I always used whatever oil I had handy, from Mobil 1 synthetic to Supertech.

[Rob92XJ]

Looks like the engine had been severely overheated in the past which would also cause the cam wear. The piston to bore clearance gets tighter when a engine is overheated and also cause the Teflon coating to breakdown.
Personally I would have not reused the old cam or lifters but that is just me.