I'm thinking I put too small a cam in my 360 Magnum...

you have the gears and stall for the cam, but with that compression and that much carb it's probably going to be a little lazy till it wakes up and gets cookin'
That's why the 750 Holley is , a vacuum secondary. I have the assorted vacuum springs kit so I can really dial it in
A Thermoquad with an adapter wouldn't fit under my hood...for now