727 or 904 in a Early A body

That's a pretty big motor for such a little car! And a itty-bitty cam to make just 415Hp. Ima thinkin she will be a terror, with freight-train torque.
Ima thinkin to keep the 4-speed and go 2.76s. First gear will get you into speeding territory in a heartbeat.And 65 will be about 2200Rs in direct. I'd love it.
35mph in second might be 2300, and in third it might be 1700rpm. With all the torque that beast will be making, I bet it wouldn't take but a little pedal, to rocket her to 65, from either starting point! And tire smoke is a sure thing.

But you asked about autos, so my vote is 904, 71 or newer,with a low-stall; like stockish, maybe 2400 at most.And a floor shifter. Because of the limited wheel size out back, you shouldn't need anything special in the tranny, but if you wanna spend some coin on it; a TF-II kit,a new over-running clutch, and HD friction materials should do it. TF-II is a semi-automatic deal.You install a few parts into your VB,drill a couple of holes and Voila! It still operates just like a stocker, but with crisper shifts, and you get to keep it in any gear til the lifters pump up!
If you do something about the small wheel wells back there, and start hooking,then a rethink is prudent.
I have never put a 727 into a 65. I had a 65 wagon with a 340-904, and from what I remember, it wasn't a tight fit.Still, I wouldn't want to speculate about sticking a 727 in there.