you must have some really big tires to be turning only 1900-2000 at 75mph with 3.73's. What size are your tires? Are you sure your speedometer isn't off?
well i have 245/60-15s on the back but my car is supposed to have a terminator t5 but i dont know....... the gear ratio is deffinatly not stock ! 5th is very high compared to the rest ! at 45mph i go to 5th and the car starts jerking at like 1400-1500 rpms !