I Chose the 383 Big Block

The Elephant ears are really good and stiff keeping the engine where it needs to be. Look into Manciniracing.com and see if they have the swap mounts.

Another header is made by TTI. They also can supply an entire exhaust system for there own headers for your car n 2-1/2 or 3 inch tube size.

The carb depends on what you’re doing with the engine/car.
A 600/650 for a grandma easy driver is fine, 750 for a little more performance, an 800 Edelbrock or 850 Holley for a beast engine.

Just treat the 383 like a big small block and you’ll be fine.
Cam it like a 318 and it’ll be great new matter the performance level sought. It’s just @ 383 cubic inches with the short stroke, a big cam is going to make the bottom rpm band mushy and even more so if the rest of the building spot on as a combo.