I read in a TG review of the Gibson SG Gothic 2 something about some models with FRs in the 80's but people had a low opinion of them.

I don't think that Esp/Ltd started making vipers till late 90s so I'm almost 99%
certain that they would have been made by Gibson. have you tried Google
a FR would be really hard to pull off on an SG beacuse the body is very thin.

A good solution is the Kahler Hybrid series tremolos. They require very minimal body routing and hold a tune a lot better then even OFRs.

As a matter of fact, I might have one put on my LP.
My Rig:(left out some stuff)
Peavey 6505 and Marshall 1960B cab
Epiphone Custom LP
Line6 PODXTLive
Electro-Harmonix Holy Grail reverb
Boss NS-2 Noise Supressor Tuner Super Chorus
MXR 6-band EQ
The Trick Thread
You have to router out the guitar body to put on a Floyd Rose....SG's are thin so take it into a good guitar tech and get ready to pay a bundle.