The right way to do it is the governor weights. Manually shifting a torqueflite, even with a shift kit, can cause fast wear on the kickdown band and high gear clutch.
I agree the governor weights is the correct way to do it but if the trans. is built right, i.e. the right combination of parts and a good shift kit (not all kits are great I'm sure you know) so as to eliminate overlap during shifts manually shifting won't hurt it. In stock form they usually overlap pretty bad (even if you don't feel it) so it isn't a good idea to manual shift but as in the case with my car I have tuned the overlap out of it and manual shift it all the time. Had the pan down after approx. 2000 miles and no clutch/band material or metal in it at all.