Hi I've got a 1990 350 manual nv3500 rcsb the motors bin mildly breathed on headers ,carb ,cam ,and modified heads it also has 285/40/17 tyres the issue I'm having is the gear change is so slow even with a hurst shifter is this just a carchistic of this transmision there's not many of these trucks here and mostly auto so it's hard to compare any thoughts?