The pylon on the inboard wing was perpendicular, i.e. hanging straight down (except on the unique pylon for the big podded radar: see http://tailhooktopics.blogspot.com/2012/11/ad-4n-aps-31-radar-pod.html). The pylons on the outboard wing panel were perpendicular to the wing instead; they were also not evenly spaced.
The outboard wing pylons were also not "swept" at the same angle as the leading edge, i.e. the most outboard one was closer to the wing leading edge than the most inboard.
The center-line pylon on the later ADs:
Note the interface with the oil cooler outlet: the forward end of the pylon is much deeper because it sweeps up into the duct (don't be mislead by the shadow).
Early ADs had much smaller and less capable AERO pylons on the outboard wing panel. See http://tailhooktopics.blogspot.com/2013/12/things-under-wings-aero-pylons.html
AD-1s through -4s had a smaller inboard wing pylon than the 5/6/7. The later, longer pylon introduced on the -5 was reportedly necessary to move certain stores farther forward for ground clearance. It also added provisions for the 30-inch lug spacing required for some stores. In addition, it may have been desirable to move the loaded center of gravity forward, particularly on the -5.
Here is a direct comparison of the World War II era 1,000 and 2,000 lb bombs on the earlier pylon.
Early ADs did not have an external center pylon so that a torpedo could be carried. The shackle was mounted within the fuselage along with provisions for an explosive cartridge that propelled a bomb downward away from the airplane when dive bombing so that it would not hit the propeller.
Illustration from Ed Barthelmes
U.S. Navy via Steve Ginter