I would also check to be SURE the "tuneup" was done correctly and a full "tuneup", not just replace the spark plugs. You need to have new and gapped spark plugs (ask the guy changing them what he gapped them to) sparkplug and coil wires, distributor cap, point and capacitor and rotor button replaced. Make sure the capacitor is tightened down properly and the distributor and coil case well grounded to the frame of the truck.
AND timed with a timing light....