I believe no C-body got the HP Magnum cam, all had same cam as the 2-barrel engines, which means same cam as 440 350hp also.
I have read that even some B & E musclecars got the standard cam if they had AC or maybe a Clean-Air package.
For a 383, I would look at a Lunati 60302, or whatever the new part# is. Its advertised duration is 262/268 (don't remember the .050" duration), but the lift is higher than most aftermarket cams of that duration, because it has faster ramp rates. But the ramp rates aren't outrageous (because it's only 262/268) so it's not going to eat valvetrain parts. I would give this cam a nod over the 40-year-old factory Magnum cam.
I actually did a bunch of 383 cam-choice reading recently, and found a lot of good forum threads, so I suggest do a lot of googling if you haven't already.
One of the premises that a number of seemingly-sensible folks said is that it's easy to over-cam a 383, and being in a C-body makes it easier.