The G-OAT ATP Picture
The GPU was a Houchin 604 GPU. It had a glorious sounding Cummins V555 V8 diesel engine fitted. No suspension worth talking about hence the appalling ride and handling.
The comment re the tractor size v the aircraft. It looks like a Reliance Mercury RM400 meaning 40,000lbs wight (18.1 tonnes in metric ) tonnes weight. I would think the ATP would weigh much the same but I agree, it does't look the right tractor for the job.