Welcome Tom!
I have not seen any of the "top" Camaro parts vendors promoting fiberglass springs and I haven't seen any project cars using them. The trend is coil over 4-link or torque arm rear suspension, which would be my recommendation if you want to take on the big boys.
I considered them 10 years ago, but ended up with Global West steel leaf @ 175 lb. I went 2" lower and added 1" blocks and it's still a little high for my liking. These cars vary a little so don't rely on my numbers. FWIW - My future plans include SpeedTech's torque arm rear suspension.