Automatic to manual conversion

IMO
A slanty can really benefit from a proper 4 speed conversion. But honestly, it's a lotta money for no cash return.
IMO
a better alternative is to swap out the rear gears for something about 30% bigger, even more if a city-car; and a slightly higher stall TC. Or just go V8; it will probably cost the same-ish and more than double your torque, while adding a buncha rpm.