My '54 Kaiser Special began stalling/hesitating going up long/steep hills about 50 miles ago. This began without any work on the engine for over 400 miles. Since then: replaced the fuel filter (old one was quite clean), replaced the electric fuel pump (old one maybe not consistently pumping), rebuilt the carburetor (float set too high, replaced a missing tiny spring), in-line fuel regulator eliminated, fuel line from pump to carburetor replaced/blown-out, linkage return spring replaced, with repeated road tests as each of these items were done. No change. Car will accelerate perfectly and run up to 60-65 mph with no problem, however, encounter a steep hill and the stall/hesitation begins. Next thing is to remove and inspect the interior of the gas tank. Any other thoughts, please.