Input needed - gears or stroke?

[goaztecs]

My brother has a 65 Mustang with a mildly modified 289. He is doing a ground-up resto, and is working on his engine strategy. He was fairly blown-away by the quotes that he got for rebuilds with a 331 or 347 stroker kit.

Knowing that his current build is not too old, I asked him "what's wrong with your motor?" In the heavier Mustang, he wants more low-end torque for off the line performance.

Since he is replacing his toploader with a T-5 with a tall overdrive, I suggested that he just swap-in a super-short set of rear-end gears. Mathematically, he should realize a huge torque gain at the rear wheels, and his overdrive will make up for any high-rpm freeway engine speeds that the short rear-end would cause.

Is there a hole in my logic? Can't he get the low-end torque he's looking for with a new rear end, and leave the motor essentially alone. Perhaps bolt-on some new heads and a cam... Thoughts???