A stock trigger should work in a 45 frame. With the safety installed turned to safe, and the gun aired up, hold the trigger against the safety. Adjust the trigger rod so that it almost touches the back of the trigger. That should allow enough movement to move the sear far enough to release it from the bolt and fire the gun.
If the trigger rod is properly adjusted and the trigger hits something on the frame before it can move through the proper distance, then you need to modify either the frame or the trigger to allow the extra movement needed.
Except for the Automag in front, its usually the man behind the equipment that counts.