Ben,

I have converted a few of the echo 21cc trimmer engines they are not hard to convert but do require some trimming of the case. I machine all my own parts from 6061 aluminum and can supply you with a prop hub and a mount if you like. My mounts are $12.50 ( Complete with screws) and the prop Hub is $15.00.

As far as the GT15T I am not familiar with that model number, But if it is a Ryobi31 cc Engine it is easy to convert as there is no trimming on the case required. I have some Hubs and mounts here for that as well. The prop hub is also $15.00 But my mount for this one is $25.00 This mount is of the standoff type and I also include the needed carb spacer. If you are interested in any of my parts email me as I check my email more often.

Scott