I'm not sure what you call an "old school" ST but if it's got a round head then it's from the 80's and was a fantastic engine. If it's got the squarish head then it's the later (current) ST. If it's the square head (latest) then it makes no difference whether it was made in Italy or China because the Italians still own the company and oversee production.

It'll be fine in a 40 trainer though so long as the model still balances where it's supposed to. My son fitted a 1.08 into his 40 trainer and it flew beautifully but he shortened the nose by 3" to get the balance correct without adding tail weight. Flying speeds (even in a dive) were kept much the same as with a smaller engine simply by using a finer pitch prop but with a much larger diameter of course.