[Jack21]

The real toss up here is 3.55, or 3.73. The decision matrix gets back to the trans gearing, and from it, what you want your cruise RPM to be.

Engine is a 351W, and it pulls like a diesel from 1200 RPM up.

The trans is a T5Z with 2.95 first, and .80 optional fifth retrofitted. Rear is 3.55. On the highway, I can put it in fifth from 40 MPH up. Cruising at 75 MPH is 2500 RPM. With a typical .62 fifth gear in Tremec's and T5's, the 3.73 rear might be a better choice, particularly with a 302. Or, don't plan on using fifth until your highway speed is higher to use it.

Frankly think the Tremec's are geared all wrong for a Cobra, and T5Z's with better gearing are underrated. A T5Z, particularly with the close ratio fifth, is great for a street driven Cobra with anything from a mild 302, to a stroker 393. In a 2300 - 2400 pound car, you can't put enough torque through the trans to damage it if you're running street tires. Even the super sticky 17" "Z" rated tires will smoke before the trans breaks.