If it wasn't heating at all before it needs more than the top element replaced. If the tank is old, just replace the whole water heater. There is no way it only needed a top element to completely fix it. If you want to squeeze a few more years out of this one, then I suggest (if it'll fit) swapping the top and bottom elements. It is the bottom element that keeps the whole tank hot. The top element is there to heat the top part of the tank (only) more quickly if you use all the hot water in the tank. If you only have the top element working, then you should notice a very short duration of hot water. My guess is you'll have enough hot water for about 5 minutes in the shower.
Many heaters from the 70's only had an element in the bottom of the tank. It is the only one that is really necessary.