You don't say if you have an inline vacuum servo (booster) on your setup, but it sounds like you may have a problem caused by having no free play in the brake operating rod that goes into the master. If you have a booster that will need to be adjusted to allow some free play onto the master piston.

If you have a plain dual circuit master there needs to be a minimum 1/16" free play in the rod from your pedal when the pedal is in the released position; if you don't have this, the brake fluid jams the brakes on when it expands with heat when you drive your truck.

Stuart.

1950 Chevrolet 3100 (occasionally working) truck:https://c2.staticflickr.com/6/5490/30684982201_6dc479d18d_c.jpg
1928 Chevrolet AB National Phaeton: https://c4.staticflickr.com/6/5573/30137792083_42886d30a4_c.jpg
1932 Austin Special Sports: https://c8.staticflickr.com/6/5793/30116567183_1520e67c4d_z.jpg