Truck Repair: i have a 77 gmc 3/4ton truck...., oversize tires, fan clutch

Question
i have a 77 gmc 3/4ton truck. with a 327 corvette eng.carter 4 barrel carb..it has two gas tanks and only one can be used to start it.  but both can be used while driving.  is there a valve switch for the tanks i should check ? or maybe gas pump?  also, over heating has been a problem, it levels out at about 225 d. and rises as soon as rpms are high. would taking the thermostat out help, or not?  just had it replaced and a coolant flush, n hoses..n didnt help...any other allternatives to keep it cool?    also  with leaf springs in front and back, dont know which way is recomended for lifting it....tires rub slightly ....want to keep the ride smooth, but also when rock climbing, want to have high clearance.  

Answer
Hi Richard,
Selector valve, or switch...in that order.
Probably not the pump.
Overheating may just be a loose belt, but check the fan clutch if there is one, and also the condition of the radiator, both fins for air flow, and internally for plugged tubes, and poor coolant flow.
I have had the heat riser valve in the exhaust manifold stay shut due to the control device for it not working, (Slightly newer model...used vacuum control), which forces the exhaust from the right side to cross through the intake manifold crossover tunnel, and will cause overheating.

You probably have way oversize tires...live with the rub. Learn to deal with it, and prevent it, or put some smaller tires on it.
Take turns across rough intersections a little slower.

Van