You will see zero improvement in performance going from a stock manual 3 speed to a 3 speed TH350 automatic transmission. In fact you will likely see a loss of performance due to lack of precise shift points of the automatic transmission.
A 200R or 700R will not improve performance at higher RPM nor on the hills. The overdrive will be nice for driving faster than 50 MPH.
The bottom line is, you are expecting too much from a 235 with an automatic transmission (TH350, 200R, or a 700R).
If you do decide to switch to an automatic transmission with overdrive, resist the temptation to use a rear end with a ratio of less than your 4.11 to 1 which you currently have. Performance and fuel mileage will suffer.
