I am picking a very nice 1970 R/T that has had a transplant from 383 to 440 6-pack with the original 727 behind it, body is pristine, rust free and gorgeous as is the interior. The car is difficult to drive with the 3.91 gears and 3 speed auto and I am kicking around a 5-speed conversion. My question is will a 5-speed conversion diminish the value of the car with the required modifications to the tunnel or increase value? I know I could do gears and taller tires, etc but I really prefer manuals anyway. TIA