Esprit V8 Gearbox

I am currently building a one off mid engined special, however I am having bother finding a gearbox with a short enough rear overhang (Porsche G50 is too long aft of the output flanges). Can anyone give me the distance from the output flange centres to the very rear of the gearbox? Assuming it is suitable, what modifications are available to the box to enable it to handle more power/torque? Been told that a quaif diff is available, uprated clutches etc but what about internals, assume straight cut gears would help but terribly noisy. Thanks