Perhaps you are referring to the Z-spec T-5? Bassicly,.. its a World Class T-5
(thats what they call it anyway.) A stock T-5 has a 3.35 first gear, wear-as the Z spec has a 2.95 ratio for first.
The Z is also rated at a tad higher torque rating. 330 FT/lbs I believe. Along with hardend gear sets, and improved blocker rings.
Its a nice shifting tranny (for a T-5 anyway). I have one in my 1990 LX.
This is the exact transmission I have, same company I purchased it from.
I had a VERRY good experiance with them.
I ordered the tranny on oct 11th of 2000.. and it was on my doorstep oct 12th. Granted, Im only one state away from their buisness, anyway I was still impressed!!
I will probably order myself a T5 Z-spec from D&D several months down the road. My T5's first and second gear synchroes are going--when cold, they grind if I shift too quickly. I'll probably get the T5 rebuild kit and just rebuild mine once I pull it out.