Bascially 3.38 (or 3.40) does not support reading a handfull of Wils (regradless if the client does or not). So lets cover each area one at a time and a way around the problems:
Weapons
The server side does not support Weapons-10, what I did myself is shove all the weapons into files 1-5 and I had to loose a couple on route but nothing major.
Helmets
Once again its the server side that seems to block helmets 2 I think, no way to do anything abut this and the helments in game are fine for me.
Mobs
Mon 1-20 + Dmon is all it supports, a case as above to shove all the mobs into these files. Some Empty spaces are not so empty and putting any mobs into these will make them all wrong. Took me a while to get the new mobs into certain wil files.
Armour
Seem to have a limit of 8 armours.
The question is, does the newest server address these issues? I know I did pass this across to 17NG as a problem and for something for him to do, this was like a LONG time ago so not sure if he fixed all of that.