So to begin we need to know where to go. First on the base weapon it is important to get a weapon WITHOUT a rail to get the balance correct. The owner needs the ability to control the weapon with either hand, so ambidextrous safeties should be added, NOT the huge flippers used in competition, but small safeties for carry. Two, it should be modified for DA/SA so that Cocked and Locked carry is not necessary. The safeties are for the range, the weapon is carried live with hammer down. Three, the tiny factory sights should be changed for really good sights, Bo-Mars or equivalent. Four, the weapon should hold at least 15 cartridges. Five, a full guide rod should be installed.
The weapon can be obtained for less than $600 from many places (GunBroker for example). It is important to get a large frame, so you want the base weapon in 38 Super, 40 S&W, 10mm, or 45 ACP.
Now from the factory order the following:
Blue Slide with Super Sight 4 3/4" in 10mm
10mm barrel 4 3/4"
DA Trigger (Chrome w/overtravel set)
Small Ambidextrous Safety
From other suppliers you will get:
20lbs Wolff Recoil Spring
Here are some of the parts in picture: