Five Speeds or Six?
In addition to the three different trim levels offered by Hurst Driveline Conversions' kits-Basic, Deluxe, and Elite-Hurst offers a choice of either a Tremec 500 or 600 five-speed, or a T56. To help Pro Touring aficionados decide between them, here's a quick breakdown of what each has to offer. The Tremec TKO 500 and 600 are an evolution of the TR-3550. These extremely stout gearboxes are rated at 500 and 600 lb-ft of torque, respectively. While the TR-3550 was designed to work in concert with meager stock V-8s, the TKOs feature larger gears, tapered roller bearings, a beefed-up case, an internal three-rail shift system with cast-iron forks, 4615 alloy steel gears and shafts, a stronger single-piece countershaft, and a short-throw billet shifter. Furthermore, the TKO has provisions for eight different shifter locations, three crossmember mounting locations, and electronic and mechanical speedometer pickups. The TKO 500 has a deep 3.27:1 First gear, while the TKO 600 has a 2.87:1 First, which accounts for the difference in torque capacity. There's also an option to choose between a 0.64:1 and a 0.82:1 overdrive on the TKO 600, while the TKO 500 has a 0.68:1 Fifth gear. We opted for the taller 0.64:1 overdrive ratio with Project Olds, as we felt the 0.82:1 overdrive was intended more for road race applications. Factoring in its strength, versatility, and affordability, the TKO is the most popular aftermarket Tremec overdrive by a large margin.

For those who need two overdrive ratios, the T56 Magnum is the new king on the hot rod block. A new and improved version of the venerable T56, this is the same transmission used in new fifth-gen Camaros and C6 Corvettes. Tweaks include larger input and output shafts, larger and stronger gears, an improved heat treatment process, a stronger case, double- and triple-cone synchronizers, laser-welded dog teeth, stronger shift forks, and shorter throws. The result is an astounding 700 lb-ft torque capacity, which is more than enough to handle the healthiest of big-blocks. For added versatility, the Magnum has multiple shifter locations, mechanical and electric speedometer pickups, and is compatible with both cable and hydraulically actuated clutches.