My '63 Ford Falcon takes a while to downshift when the engine's cold, it's an automatic trans. (more)?

Have you checked the ATF (fluid)? It needs to be checked after the engine is warmed up, in park, on flat ground w/ the engine running. The filter prolly needs changed bad as well.The exhaust leak has nothing to do w/ loss of power. The fuel pump is prolly good BUT change the fuel filter as it can be part of the problem. ALSO check the vacuum line that goes to the modulator valve on the side of the - it is a vacuum hose running from the engine to the - it causes the to shift- the modulator valve could be the cause or a split in the hose, causing a loss of vacuum.