I'd recommend a lower gear with an overdrive, the 3.55 is a great highway gear as it is. I bet with the 4 speed it is sluggish off the line, but cruise is just fine, as it is 70 mph is around 2,600-2,700 rpms with 3.55 depending on tire size. 3.73 is better, but the rpms will be a bit low at cruising speed in overdrive. Although, Texas cruising speed is 80 and higher, so you should be good. If you could find a 4.10 or 4.11 geared rear that would be better. Nothing wrong with improved braking, so disc all the way around isn't bad. I don't have any recommendations on suspension kits.
