carb problems

i have an 85 ranger 4x4 with a 2.8 auto. it hasn't ran right since i bought it. has no power and usually won't stay idleing. it's runnig rich and i have tried to adjust the air/fuel mixture but no matter how much i turn the screws it runs the same. i just changed plug wires, pulgs, cap, rotor, pcv valve, and fuel pump. i rebuilt the carb. i can rebuild them i just can't tune them. timing is dead on and all of the vacuum hoses are good and hooked up correctly. any suggestions. and can someone please tell me how to tune a carb. i'm used to working on fuel injected vehicles.

sell the truck and get a 2.9 motor, the ford 2.8 v6 motors are junk

been a while since i checked this.  any other suggestions.  i know the moter is juck just don't have money for a new one.

Have you check the float (inside the carb) to see if it is setting level and the fuel pressure (too much fuel pressure will cause a rich condtion on carb motors it will excede the shut off pressure of the main fuel needle and seat) from what you discribe about adjusting the screws (the bench setting on carb for the idle adjustment is to seat the screw lightly not too much pressure or it will distort the needle and seat is to turn it back out to 1 and 3/4 turns) does the truck have a return line to gas tank? if it does it might be restricted and causing high fuel pressure just my thoughts on the subject, good luck with the truck