What is the best way to get a GLCode attached to either an Item or a PO?

I am trying to join one of the following tables to GACCOUNT. PORDERQ or ITMMASTER. There doesn't seem to be many ways to get from GACCOUNT to an ITMREF_0 or POHNUM. 

I have tried a few different options but none seem to be working. Your help, as always, is greatly appreciated.