Sorry, I'm not willing to discuss this subject with a home owner.
You may think this is a "simple" piece of equipment. But let me assure you that you are not able to recognize all the hazards involved.

What I am willing to advise you on is this!
You said you paid very little for this lift. Do yourself a favor, look at new chair lifts and what they have to offer. Ask a chair company what the safety improvements they have made in the industry since your was manufactured. Then ask how much one would cost to have it installed in your home.

This may not be what you wanted to hear. But it is intended to be in your best interest.