if you have the truck on jack stands that's good.
you can try turning the steering housing so the opening points underneath towards the front, you may have clearance for the axle in that direction. Use the hole in the frame after you get the retaining nut/snap ring off the axle to put a long enough bar through it and knock the axle out that way. Get a floor jack under the tire to take the pressure off the axle and it should slide out easier and will also catch the tire.
the only other way is to drop the steering unit out.