Hi, Ozzy! Welcome!
Here are some specs I found in an ad for a 2000 Coachmen Mirada 300QB recently for sale. I don't know if this is the model you have, and this has a Chevy engine in a WH chassis, but it might give you a start.
Specifications:
Chassis: Workhorse
Engine Manuf: Chevrolet
Engine Model: 7.4L V/8
Fuel Type: Gas
Sleeps: 6
Water Capacity - Black: 35
Water Capacity - Fresh: 95
Water Capacity - Grey: 42
# Air Conditioners: 1
Air Conditioner Spec: 13,500 BTU
GVW: 17,000
Dry Weight: 12,172
Payload Capacity: 4,828