Hi and thank you for your question.
I cannot find a company that makes any kind of conversion for your bike to a trike. The problem is, the companies that make trike and trike type kits have zero demand for a kit to fit a 1983 motorcycle. The sad reality is they have to have enough of a demand for people wanting to buy the kits to justify the expense of designing, testing, tooling up and mass producing them. The other sad reality is there are not a lot of 1983 Maxim 650's on the road any more. What few there are still on the road, only a very small percentage of those owners, you, want to convert it to a trike. All of that adds up to bad news for your original plan. However, if the motivation for wanting a 3 wheeler is to have a motorcycle that will not need to be held up when stopped, I would suggest putting a side car on the bike instead. There are a few advantages to that. A.) Side cars tend to be a bit more universal in fitment and therefore easier to adapt to various motorcycles. B.) Sidecars, and possibly used sidecars, are going to have a lot better availability than a trike kit/conversion, which is all but non existant. C.) A side car would be tremendously less expensive to purchase than a trike kit. I saw one conversion for a trike kit that was $4000 by itself. I assure they can go up from there, that was by no means the top of the line trike kit.
The downside to both trikes/trike kits and sidecars is there is a definite negative impact on handling. As much as the trike companies would have you believe otherwise, you are going to feel a difference riding a trike or any type of 3 wheeled motorcycle over a 2 wheeled motorcycle. They just don't turn as easy or the same. They are not un-rideable obviously, as noted by their popularity, relatively speaking, but those riding them are willing to accept that trade off to be as close as they can be to the experience of riding on 2 wheels.
If you have any more questions, feel free to ask.