How do I pull the oil pan in my 1987 b2600 4x4

That should be a Mitsubishi engine in the 1987 B2600......and I have not messed with one of those.....yet. On the 1989 through 1993 B2600i trucks, the engine is a Mazda 2.6 motor, and those you can remove the oil pan only, as long as you have the needed clearance between the oil pan and the steering drag link.......you may need to unbolt the Idler Arm from the side of the frame rail, to lower the drag link and gain some room.

I am not sure how the oil pan is on the Mitsu engine though.