What's needed to fit a 440 Six Pack under stock hood

I believe many have done it without modding the hood. My '69 Barracuda didn't need it with a '67 or the '69 hood. Spacers under the cabs ain't gonna' happen unless you're cuttin' though.
DO NOT install the air cleaner hold down studs until you know your clearance!
Do notice the wiper motor in your picture. A two speed will require a notch in the air cleaner base. If you have a "shaker" base, all it needs is a small bend.

BTW, I recommend a torque strap.