All metal parts of the service must be bonded to the neutral, so you'll have to bond the gutter with a jumper to the neutrals. Each metal pipe nipple must be bonded (at one end), either with a grounding locknut that does not encouter any remaing cocentric/eccentric knockouts or with a grounding bushing with the proper sized jumper . Finally, each panel must be bonded, generally using the screw or wire provided by the manufacturer.
