What are you trying to address w/ the stock convertible setup?
For me, I enjoyed the car for casual drives w/ the stock suspension, but it was an absolute boat for any type of performance driving, particularly for autox. I changed to the Ford Racing Track Handling Package. I installed this...
I have a full set (shocks, springs, sway bars, traction rods) from a 2015 manual gt convertible, removed @ around 10k miles. Located in Irvine/Costa Mesa, CA (South Orange County). You can have it for $20. The only condition is that you have to take it all.
The same guys who set up the autox's @ SV events are running at Big Bear Airport next week:
Cooler weather & a bit more design variation compared to that inside lot at ACS. I will be there Saturday, not in my Mustang, though.
As long as you are just wanting to have fun, the convertible is great. Since my race car has been down, I've run my GT convertible at several events as-is (even w/ the stock pirellis). It's very predictable and works okay as long as you plan ahead (turn-in & transitions are not crisp w/ stock...