Sub panel connection for Grid Tie system?

[skipparks]

I am confused about hooking up my PVPowered 3500 Grid Tie Inverter to the sub panel in my garage. My home was built in 1975 and the sub panel is wired to the Main panel with 6/3 romex, no-ground wire, at 240vac with neutral wired to grounding block at main panel. My question is, will I be allowed to wire the GT Inverter to this sub panel for my ac connection to feed the solar power to the main panel? I will be grounding the solar panels to the inverter and then to a ground rod at the inverter location. The sub panel ONLY feeds a 240vac outlet in the garage, NO 120 vac connections from the sub panel and the 240vac outlet will be abandoned before the system is charged. The sub panel neutral is connected to an isolated neutral block in the sub panel, So my only ground will be to the solar panels connected to the DC ground on the inverter and inverter to the ground rod. I am hoping the the grounded neutral at the main panel can be disconnect from the neutral grounded bus bar and connected only to the equipment ground bar at the main panel and will be sufficient for grounding the AC side of the inverter. So the short of it all is: can the white neutral wire be used for the EGC wire that is only connected to the ground buss bar at both the sub panel and the main panel instead of using a solid ground wire? Any info will be greatly appreciated, and thanks for looking.

I found the answer to my question and I'll post it here due to the lack of any replies:

NATIONAL ELECTRICAL CODE

ARTICLE 250

GROUNDING AND BONDING
250.118 Types of Equipment Grounding
Conductors.
The equipment grounding conductor
run with or enclosing the circuit conductors shall be
one or more or a combination of the following:
(1)
A copper, aluminum, or copper clad aluminum
conductor. This conductor shall be solid or
stranded; insulated, covered, or bare; and in
the form of a wire or a busbar of any shape