Autos aren't too bad, they just aren't really a platform for performance build ups. I don't think you will get your money's worth for the list you have there. You are talking about spending much more than the car is worth on upgrades. The auto tranny won't last too long without some major upgrades either. However, since you are the original owner you would know better how it has been treating you. My true advice would be to buy a second, higher mileage MT TT car to build and keep the low mileage AT one just that.