Just got myself a 68 Barracuda Fastback!

For a streeter and a stick, the 360 is all you need; unless you want to stuff in some hi-way gears.Then the 408 is the way-to-go.If it was me it would be a 360,a 5speed,and a starter gear of between 10/1 and 11/1.
A streeter has an easy life; it only has to 60ft reasonably well, and be able to hit between 50 and 60 at the top of first-over; heehee. And it's nice if you can go home for Sunday-dinner at less than 3000 rpm.
Having a 408, means 3.23s are doable; and that means you can put a teensey-weensey cam in her, to hit 60 at about 6200,Shazzam!
You are gonna need some serious traction aides.
3.23s will cruise 65 at a tic over 2500 with 28s
360s need not apply.