GFCI on all ac circuits: Still ground all receptacles?

[marant]

I am planning out the wiring on my CT and have a question about grounding the AC system when using GFCIs. I will have two 20 amp and one 15 amp circuits, with a gfci on each circuit which will protect all downstream receptacles. I know a gfci does not require a ground to operate properly, and it appears that grounding each receptacle is not (or at least was not) required by the code, but that pertains to residential construction. Does a metal trailer have other needs to be safe?