Among the range of available parts for the popular AAP01 from Action Army, everyone should find something for themselves. Sticking only on the external parts, one can replace adapters, magwells, enlarged manipulators, metal receivers, conversions kits changing the gun into a drill or a blaster.
The AAP01 itself is quite far from the Ruger Mk.IV, which was definitely an inspiration. However, one can make the replica look more like a real firearm. Thanks to the Narcos frame, you can feel the grip known from the 1911 pistol in one's hand.
Replaceable grip panels (which are not found in the stock AAP01) can certainly be replaced with something more comfortable or visually matching. However, a proper fit will be required due to the double-sided bolt catch. In addition, when using this frame, one will have make some sacrifices: no manual safety above the trigger, it will not be possible to move the magazine release button (added to the set, smaller than the factory one).
The remaining functions of the replica remain unchanged. Narcos Airsoft R Style ABS Lower Frame is currently available only in black and costs 31 USD in one of the Asian stores. Of course, shipping and other costs must be added. Anybody wants one?