There is a sphon tunnel mounted torque arm for a 93-08 Camaro listed forsale locally to me. It is brand new and a good price. The seller says it will work on a 85-92 with slight modifications.

What modifications are needed to use this on a 3rd gen, if it can be done at all?

Call sphon. And ask them...to be sure

It wont work, crossmember totally different and I believe the length is too.