Stole it because it was easy to copy and past but i agree with these thoughts.
Sounds like your engine has not been redone as in machine shop redone and is original. And you plan is to keep it that way.
"In my opinion, you can but you shouldn’t. If you have an engine that has been running on a non-detergent oil for years it could actually damage your engine to switch to a detergent oil. You see, after so many years your engine is going to have sludge and contaminants built up within it. By switching to a detergent oil it could cause the sludge to break apart and be released throughout your engine. This could ruin several things from rods, cam shafts, bearings or anything in-between. The movement of the sludge overtime can clog your engine lines and cause serious wear on the engine. If you have an engine that runs healthy with a non-detergent, the best thing to do is keep the oil consistent.
It is important to break down the misconception that all non-detergent oils are bad. Non-detergent and detergent oils both have their benefits and downfalls but each application is unique. It’s all about making the right choice for your engine based on what it needs."
so if you need is just keep it running then go with what has been used for years.
If you machine shop that thing to new and replace all the hoses, lines etc then well you can go either way.
