If you used the stock motor mounts on the OEM 383 A body cars made form 1967 to 1969 the 402 pan will hit the steering cross bar, been there done that
The original pan for the A bodies where stamped 890 I think, not sure if they where for all 3 yrs or not though
I used the 1965 to 1969 C body pans and welded in acceleration and deacceleration baffles in them
they will hold 5 quarts easily, some guys have ran them with 6 quarts in those pans also
Those oil pans look a lot like the stock 1966 to 1969 Street hemi oil pans also, one of them may fit also
I never tried one of them in A body due to there resale value
As far as adding oil restrictors you can add them into the oil passages in the heads, I would remove the heads and drill and tap that passage for either a #6,#8 #10 or #12 thread size for using a blank brass set screw in one of those sizes, which ever fits the best
I use a .042 drill bit size in the set screw to make them flow oil
that size works well on roller rocker, I would use a bigger hole for non roller rocker though, probably around .080
I normally restrict those passages in the block, while building the motors I don't remember what size set screw to use now though
I use #6x32 blank allen head brass set screws in carbs to restrict the fuel delivery to lean them down in the idle and transition fuel delivery circuits