The chassis IS grounded. There is a large ground cable run to the motor plate from bus bar and each cylinder head is tied together. Of course the motor is solid mounted, so this automatically makes it grounded to the chassis.............BUT, you are NOT using the chassis as a main ground path. The chassis is actually a very poor conductor, but most use it as their main ground path. Have to remember, motors and such are mounted TO the chassis usually through painted tabs and bolts. That's a POOR conductor. Some have studs welded to chassis, that's fine, but other parts are still bolted to chassis, NOT part of it

On the car pictured, the ONLY things I have grounded directly to chassis itself is the rear lights, the shift light and the Race Pak. All "noisy" items are on the bus bar and separated. The ECU power and grounds go directly to battery. I have wired all EFI cars like this since I started and do not have RFI issues. If it's good for EFI, it's good for anything