There will always be a tradeoff between accelleration and economy with the Z transmissions. If you have a 3.36 or 3.54 rear then you definitely want the early 280zx 5-speed with the 3.21:1 first gear or a T-5 with the 3.5:1 first gear. If you've got a 3.7 or 3.9 rear then using the early 280zx 5-speed will result in fairly high rpms at cruise, but awesome accelleration. The T-5 has the best all-round ratios with good accel and a good overdrive. If you've got a 84-89 300zx trans lying around then you can swap the overdrive gears from that into the early 280zx 5-speed and get a really good overdrive, like around 70mph at 2750rpm. The overdrive gear is the only gear in the z trans that will swap as the 1st-4th gears are a one piece unit on the countershaft side.