1995 diesel 6.5 draining batteries?

Hi Everyone, I am asking for some information .
helping a friend with a 1995 dually with 6.5 diesel dual batteries, when it sits for a couple of days it will drain the batteries. when I run my multimeter in line on the passenger side battery with drivers side still hooked up I have about 350 ~ 400mA current draw, Pulled all fuses and still has the same amount? disconnected alternator,no change,any ideas , and what should the truck draw while sitting?
Thanks

Probably get an answer here ... ---> <---

This looks like a maybe

I will give it a shot....said drain should be < 50mA stock.