You might want to look into an E40D. It was an evolution of the C6. It's the only overdrive automatic transmission that will bolt directly to a 385-series engine.
It's basically a C6 with an overdrive added to the front, and is fully electronic - needs an electronic "brain" to run it. There are a couple of companies that make such a brain-box; they're around $500 and are easily programmable. I am setting up just such a system using a similar, smaller late model Ford transmission behind a Shelby 497 FE, for a customer car.
There are two great things about these kinds of transmissions. One is the programmability; you can set the shift points and shift firmness across a curve, meaning it will upshift softly and at low rpm at light throttle, shift hard and at high RPM at WOT, and so on. The other is that you can run, and control, an electronic lockup torque converter. Free (relative term
) power to the rear wheels, free fuel economy, lower rpm at cruise... nice deal.
The only downside to the E40D is that it is rather huge. There
are alternatives; talk to your transmission guru.
Chris Weisberg
Carroll Shelby Enterprises
P.S. Transbrakes are for hard core drag use! If you don't have traction (as in, most Cobras) a 'brake is rather pointless. If you do have traction (slicks and traction device(s)) and use a transbrake, you will need a beefy drivetrain. A 'brake gives an extremely harsh application of power; it's not like "powerbraking" and then releasing the footbrake. I myself don't relish the idea of the jagged end of a driveshaft or halfshaft flopping around ventilating the underside of the car as well as my ass. Most companies don't offer a transbrake on a street (i.e. non-manual valve body) transmission anyhow.