I would recommend finding some carburetor books to read. People have made careers out of this question and it cannot be answered in a few sentences or paragraphs.
"Holley Carburetors & Manifolds" published by HP Books is a good place to start.
Kyrasis6
Mazdatruckin.com
a webber, is a type of holley carburetor.
Holley 4180
There is no reason you would have to.
holley 4150 c
You will need an adapter to coveg the EGR crossover.
To install a Holley carburetor on an Edelbrock Performer intake, first ensure the intake manifold is clean and free of debris. Use the appropriate gasket for the Holley carburetor and align it with the mounting holes on the intake. Secure the carburetor on top, tightening the mounting bolts evenly to avoid warping. Finally, connect the fuel line and any necessary linkages, and double-check all connections before starting the engine.
Yes, it's the Holley 1940. You can get them from Champion Carburetor.
A small one with vacuum secondaries.
Very little, if any at all. The carburetor is not what makes the horse power, The rotateing system and Valve train is what makes HP.
On a Holley four-barrel carburetor, vacuum lines typically connect to specific ports for various functions. The manifold vacuum port, often located on the front of the carburetor, is used for vacuum advance on the ignition system and for power brakes. The ported vacuum, which is usually found on the side of the carburetor, is used for accessories like the ignition advance that only activate at higher throttle positions. Always refer to the specific carburetor manual for detailed port identification and usage.
The Holley website has an interactive carburetor selector (see related link). Holley doesn't make just one product, as there were several engines made without Electronic Fuel Injection - thus, they make a range of products for different engines.
If you do have a 351 cu. in. go with a Holley replacement, and even look at a throttle body, and if you have a few extra bucks, check for the port injection from Holley.