GM-GMC: 1993 gmc sierra, gmc sierra, rear shoes

Question
when i apply the brakes the truck will pull to the left BAD. i just put a new caliper on the passenger side and it still does it

Answer
I would check all four wheels.  If the left front caliper is partially seized it could cause what you are describing.  Same with the rear, if the left rear is grabbing it can cause a pull.  Make sure all the slider pins are clean and moving freely, rear shoes are adjusted correctly.
Hope this helps.