When those ST engines were popular, quite a few guys just mixed a new gallon of 15% fuel with 3 quarts or so of Methanol to get the desired low oil mix. If you decide to run the engine, don't even try to use the ST glo plug if one is provided. I don't know of anybody that was very successful using those. I preferred a plug such as an Enya 3, OS A-3, OS-8. Some guys liked the OS F plug but I had better luck with the Enya 3. These engines also liked a traditional idle bar plug but avoid a FOX plug if you go this route. If you have a problem with this engine, it will probably be flame outs and of course they never happen at a convenient time.
Another point against those old big ST engines .... I always thought they were real shakers. Especially compared to most any engine available these days.