Here are some specs:

Length x width x height: 490” x 96” x 134”

Gross weight (GVW): 13.476 tons  

Engine: rear-mounted, 8-cylinder, GMC model 8V-71 two cycle diesel

Luggage compartment: 345 ft3

Output: 245 hp

Passenger seats: 43+2 seats

Electrical: 12vdc with two batteries Chassis Three-axle

Air Conditioning: 71/2-ton carrier unit off main e

Fuel tank: 180-gallons

Brakes: Air brakes Bendix-Westinghouse Gearbox: 4-speed, manual

Taken from: http://ttd.cernun.net/newgrf/longbus.html and spelling corrected.

Thanks guys that is exactly what I was looking for.

The bus was built by GM as a PD-4501
and modified by Marmon Herrington
I saw one several days ago done as a motor home and was impressed.  The owner was at the Royal Canadian Air Force Museum and was donating some of his artifacts.  By the time I got back he had left so I never had a chance to speak to him about his bus/motorhome but it sure looked impressive.  Would not have minded having a peek inside either

Again much thanks for your efforts.

Cheers...Happy Landings...Doug