I have a 2000 Chevy Express 3500 van that I want to convert to 4x4. I am looking for any info to do this. I prefer to have r.h. front driveline as to not wanting to shorten my fuel tank if possible. I need specs: steering linkage, spring mounts, front diff, etc. I understand cost vs buying a new vehicle, but I don't want awd. Any info is appreciated.  

This is strictly an idea I have no real exp converting vans to 4wd. Im sure someone has done it but good luck finding someone.

You could do a solid axle swap. You would probably be looking to run a 4 link style or an extremely flat leaf spring.

There is also the possibility of using late model 4wd chevy parts. Knuckles front diff etc. All of this would be an ifs setup.  I don't forsee you rock crawling an express 3500 van. You could use an older transfer case like a 205 which is already set up for a right hand drop. You would need to find out what current trans you have and find a 4wd adapter for it. Usually this means changing your mainshaft in the transmission. For mounting the diff you would have to make your own brackets for it no matter rhd or lhd. I would look to use existing chevy pick up cv axles only your left on the right and the right on the left. Due to wms to wms measurements I don't know if these axles would work. Im not sure of the cost of custom cv axles.

There is also the option of buying a running chevy truck and mount the van body on to it. It seems like less fab lol.

If you can give specifics of what your transmission is it would be easier for me to look into the possibility of mounting a tcase behind it. There is about 900 million more things to investigate. Like frame widths and so on. If you do go into it head first take lots of pictures and post them. Id like to sit behind my computer and watch.  

You do not even want to use current tranny anyway regardless of tail shaft swap. 4x4 trannies have stronger, thicker cases to control Tcase counter torquee in low range and keep it from twisting rear of tranny housing off.