Sorry that much I knew guys, AFAIK the 16g is the 60mm and the 16g6 is the 68mm as far as model numbers go.
I think the T517Z is also a TD05-17c but I would need to look into that again.
The SR in question is an internally standard S13 SR20DE in every way. Will be running Nismo 740s, Z32, Walbro, 450mm china core, 3" tbe and a Nistune. Has been running on a factory T28 and DET tune at 11psi/183rwkw for the last 6 years so the update will be interesting. We are aiming for 250rwkw and it will be tuned at Unigroup.
Theres a guy with an SR in a E36 on youpoop that had a T517z and went to a T518z, I cant remember if he commented he lost a little response or gained a little peak yet the vise versa was unchanged.. I think it was that he lost a little response but I honestly forget. The big T518z cars i see all run 10cm rears on SR's..... Interesting concept.. I myself am dreaming of putting an Evo TS variant on mine (S15 10:1 CR SR20DE), that would be truly dangerous.