dual tanks came as standard issue on a 1989 ford f150,, after jumping back and forth looking at the 88, 89 and 90, I'm leaning on it being a 90. and I know someone will say "but le said it was as 89?", and my answer will be "le also stated dg as having blue coloured eyes".
A 1989 ford f150 can hold 37 gallons at max capacity/topped off and get 17 mpg with regular gas (probably more with the slightly higher octane now but not the highest octane),, which translates to 629 miles or 1012 kms. We'll stick to 1000kms.
So lets do a radius chart; after filling at dg's and then travelling to the l's then back to dg's (assuming he went there), how many km's did he burn and how far could he get to wherever/radius and back to his property without refueling after returning to his property?
After some realistic averaging, DG travelled 80km's and I'll add another 40 km's for random driving, so 120 km's,, which leaves 880km's remaining or 440 km's he can travel away from his property and back without refueling.
DG could travel to Edmonton or Sakatchewan or The US/Canada border and back without worry, even less worry if he brought along two 5 gallon gerry cans. But would he want to travel QE2 North, Hwy 2 South, Transcan East/West, Hwy 22/Cowboy Trail N/S or Hwy 9 Drumheller, or the corridor's of white knuckle driving on a holiday weekend?
The heaviest presence of LE's on Canada Day are West/The Old Banff Coach Road/, Transcan West, QE2 North and 2 South. The closer you go towards Sundre/Rocky Mountain House the worse the random stops by the RC's. So this leaves going East or South East