Your 3.55 gears will make a difference and adding a TH-350/400 will also make a big difference. I have 3.73 in mine and had a TH400 and the gears alone made the car move much quicker off the line, but highway speeds were almost unbearable since i was running about 3100 RPM's at arouns 60/65 MPH. I put in a 2004R overdrive tranny and the gearing is a lot better. The car launches faster off the line now and highway speeds are down about a 1000 RPM's from what they were with the TH400. I have copied and pasted some gearing info below so you can have an idea of what the gearing difference is between trannys and help you decide what way you want to go. GM Automatic Transmission Gear Ratios Transmission _Model----------First Second Third Fourth Powerglide.....1.76 or 1.82 1.00 TH-200-4R......2.74 1.57 1.00 0.67 TH-350...........2.52 1.52 1.00 TH-400 ..........2.48 1.48 1.00
