No fuel is getting to the cylinder, if there is good spark, assuming you checked the plug, wire and distrubitor. If spark is good right at the plug, then the intake valve is stuck shut.
There is no reason you would have to.
You need to go back to the basics: Are the plug wires connected properly? If they're out of sequence (at the distributor) you'll definitely see what you're describing. Have you checked the individual plugs? Are they fouled? Wet? Is there a vacuum leak that's making the affected cylinders a bit too lean? Beyond that, it's just a matter of isolating the problem and attacking it one step at a time. Good luck.
a webber, is a type of holley carburetor.
Holley 4180
holley 4150 c
You will need an adapter to coveg the EGR crossover.
Yes, it's the Holley 1940. You can get them from Champion Carburetor.
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 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.
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.