I have done this SO many times in my short WB 77 van, I can do it with my eyes closed. Big block or small block, they pull the same. Mine originally was a 360, now it is a 440. I got good enough at doing it where I did quite a few other vans, swapping engines, rebuilding and the like.
If you remove the grill by taking the little plastic tabs out of the top, and two screws just below the turn signals, you will see there are about 6 screws holding in the entire radiator support. You remove those screw and the entire front comes off in one piece after you remove the radiator hoses. You pull the motor through the front. I tried it through the pass door once, it takes at least 4x longer.
If you have a BB with AC, you may need to remove the valve cover and valvetrain on the right side, one Motorhome I pulled the motor on I had to pull the right head.
In either case, the exhaust manifolds need to come off, as the intake/carb. This is beacuase the clearance is tight, and you get a few precious inches without the intake. Make sure the picker is as tight to the motor as you can get it, tighten it up, kill the motor mounts, and pull away. You do not have to remove the pan, and the trans can stay there. I have a piece of square tubing, about 2.5 feet long, with a hole in the middle that I thread a tranny bolt into to support the trans with the engine gone. I do this by going across the floorboard on the inside.
Obviously, the normal things like fuel lines etc need to be disconnected, and the throttle linkage I found should be removed at the firewall. Anyone wanting to convert to a BB, with a 76-79 should find all they need is some headers, a right hand water pump housing, and the proper big block mounting brackets. Everything else works inc the factory radiator and motor mounts.