hoses
Hello Jackie,
Sorry no one has given you an answer on this yet. I was waiting for someone to answer but it appears as if your question may have gotten overlooked.
You have a valid concern to make sure your vintage dishwasher doesn't leak before installing it.
Most likely, GE used a rubber hose for a drain line back then. I would check it for cracking and brittleness. A new plastic/vinyl drain hose is relatively inexpensive and they are available at Lowes, Home Depot and Ace as well as many other home stores. It might not hurt to just replace yours with a new corrugated hose.
There is also a hose going from the water inlet solenoid valve, under the machine, to the fill opening on the side of the machine. Machines in the recent decades have used a flexible rubber or polymer tube. GE most likely used a rubber tube back then but there is some possibility it could be a copper line.
Look on the outside of the tub of your machine, you should see a tube running from an opening in the side of the tub and going under the machine. Once again, if this is a flexible tube check it for brittleness and cracks. To play it safe you might wish to go to Lowes, etc. and get a tube (capable of handling hot water) of the same diameter.
If your machine has the "Power Shower" that sprays down from the top of the tub onto the upper rack, you will also find a hose running from the pump, under the tub to the top of the tub on the outside.
So you have the potential of three external hoses that you may wish to check/replace.
If you can, I would replace these and then put your machine in a garage or basement, where no damage will be done if it leaks. First pour some warm water into the bottom of the tub and let it stand for several hours or even better, overnight. Hopefully this will remoisten and swell the seals. Look for leaks.
If none, and you have the capability to hook up the drain and water inlet, see if the inlet valve or inlet hose leaks as the machine fills. Check for leaks when it drains. When the machines is running check for leaks in the tube to the power shower and check for leaks around the door.
If all is dry under the machine, then I would say go ahead and install it under your cabinet and ENJOY!!