I agree with your Dad, stroking is a waste of time , especially with a 289 when there are 302's and 351's stacked like cordwood at every wrecker in the country.
For a transmission upgrade, get a T5 overdrive out of a newer 'Tang , or a toploader 4-speed if you can find one that's priced reasonable.
Don't go overboard on the cam. A small engine can't stand a lot of duration, it'll turn into a peaky "dog" with no power at all unless you scream it, not the best on the street.
Good luck on your car,sounds like FUN!