Can anybody with a xxx chassis tell me if the gap under the motor plate is normal?

The gap is normal nowadays for weight savings. The floor pan usually wraps up the front to take up the gap. Typically the lightened side of the motor plate gets installed facing forward though.

All the XXX motor plates have the lightened side towards the driver, and you can tell by the groove across the top of motor plate where the dash (aluminum or fiberglass) resides in. We have new and used XXX motor plates available, along with frames, bodies, and other XXX items. Thank You.