There are very few T300 speed triples on this site. We banned the last one that joined. I'll get howled down for this, but there is a forum dedicated to the T300 models on Trat. There are some very knowledgeable owners there who will have some answers for you. I have a 96 speed triple, and thats where I go when I want help.
I'm pretty sure that the rearsets for the later models will not fit your bike.