Thanks for that additional information.
I understand your concerns about what the engine actually is, BUT . . . the things that make the engine a "383HP" are inside the block rather than the block itself. Just like the differences between a Chevy 350/300 in an Impala and the same engine in a Corvette. In this case (SBC, the block can be either a normal 2-bolt main or 4-bolt main, due to horsepower levels; something that does not exist in the realm of Chrysler non-HEMI B/RB engines).
What makes the 383/335 what it is include: The camshaft (for the additional power), the windage tray (for power and oil control), and the roller timing chain (for durability and timing chain longevity). Same pistons (but with allegedly a Moly-coated compr0sesion ring). Allegedly tri-metal bearings for the crank to run in All compared to the normal 383/330 motor, as mentioned in the Dealer Data Book of specifications and features.
End result, the camshaft would be the ONLY real thing to be concerned with, to me. The only thing which could relate to an NHRA power factor to increase the 335 power rating to something higher. Of course, depending upon the class you want to run in, the cam would be removed anyway. As might the existing carb and distributor calibrations.
The "HP" stamp on the block is merely for assy line purposes, to ensure it gets the correct camshaft and pistons in it, for an upgraded 4bbl build. Just as the "hourglass" water passages on the heads deck surface. These were mentioned as being on HP and Motorhome blocks, for better water flow, BUT when you consider that only ONE side of that hourglass actually flows water, due to how the head gasket sits on the deck surface, those "hourglasses" quickly become ONLY a visual identifier of a RB440 MHC ("440-3") engine build.
SO, the more I was around my late machine shop operative, seeing engines day in and day out, the drag race engines, worn stock engines, and everything in-between, when they are all nekkid to the world on the teardown/rebuild table, what makes an "HP" engine what it is, especially a non-HEMI B/RB engine, is what's inside the block.
In looking for a new cam, COMPARE the actual cam card duration and lift specs against what the OEM specs were. EVEN IF the cam comes from the Direct Connection/Mopar Perf catalog listings! If it supposed to be an accurate repro cam, the specs should be the same as the OEM-production cam, period. NO MATTER what they call it, the specs should match exactly.
I mention this as the only REAL "Purple Shaft" cams were the 284/284 Street Hemi cam and a larger 292* cam. Maybe one larger? In later times, MP co-opted that "Purple Shaft" designation on a complete LINE of cams (probably co-opted from what used to be Crane Cams?) I wanted to mention this as a point of clarity in the usage of the "Purple Shaft" name.
These are all things I've observed over the past 60+ years as a Chrysler enthusiast. I'm NOT an expert, though, as those more involved have probably seen other things, too. YMMV
Having mentioned these things, enjoy yourself!
CBODY67