75 200 carb and stalling

Just to make sure I mention....
These early TBI systems controlled EGR, and had inputs from knock sensor, too.
The knock sensor is another "screw in" sensor that GM put in their block drain near the starter on the V-8s. The 4.3l V-6 is just a cut-off V-8 in appearance.
We know A LOT more now than we did then about EGR and knock sensors.
You should really consider incorporating the EGR system somehow. It lowers cylinder head temps (helps stop engine overheating) AND it increases fuel mileage because the GM ECM EXPECTS a certain amount of EGR flow in it's calcualtions.

TBI has all the dis advantages of a carb, and almost none of the advantages of fuel injection. I wouldn't bother, either keep a carb or do a full fuel injection conversion.
TBI suffers from carb ice, it still relys on heat from below to vaporize the fuel (injected at a low pressure so doesn't atomize). It does work, but not as well as high pressure port injection. Just my 2 cents worth, haveing delt with them when they came out. Carbs are simple and can work quite well, need no special fuel pump or signals from the engine and no "sensors" required.

Again, time has moved on and left you, CB!
TBI is WONDERFUL!
Just to remind you:
1) point ignitions are outmoded.
2) 6v systems went out with "fins" on cars.
3) fuel injection is not a fad. It's here to stay.

BTW, I wish I could've apprenticed with someone like CB years ago! I'd be a superstar!
The "he's forgotten more than I'll ever know" saying applies here!

Here is a thought: http://www.hamiltonfuelinjection.com/
Some of us are not real fond of "newer Tech" But others are.
Now pull in the Claws fellows!

I made nice.

All I was saying, was if I were going to go thru the trouble of modifing, I would go all the way (port fuel injection) or not bother. It is MY opinion that TBI doesn't solve enough to be worth the compomise, other may differ. The are essentially a "pressure carb", still carburateing and not atomizing the fuel the way port injection does.

You are extremely knowledgeable about which you speak, CB.
What TBI does that a plain carburetor does not, for one thing, is LEARN.
It's considered "elasticity".
That just means altitude and barometric pressure can change significantly, certain sensors can degrade, cylinder and manifold pressures can worsen, vacuum leaks can appear and even driving styles can change. The thing just RUNS. Good.
Carbs can't do that. They're not considered "elastic".
A multipoint FI conversion is a very involved and expensive operation. Yes of course it's better than TBI.
However, TBI is becoming more and more of a "bolt on" as old vehicle lovers discover they can rid their vehicle of a lot of driveability problems by adapting one.
Once again, they're anvil-solid systems as witnessed through millions of older TBI trucks still on the road today.
(I know because I have to smog them).
Having stirred the pot I would advise anyone who was going to try to adapt TBI to go online and research what happened when all the other guys tried it FIRST.
Once again, I respect your huge knowledge CB!

OMFG!

Why do so many threads on this board go "off track"??? The OP asked for a direction to follow to find and fix a few simple issues. Can't we just KeepItSimpleStupid?

First, I guess I missed something? I see NO mention by the OP of any carb. but the Holley 2300 that is on the vehicle.

The reality...
There is absolutely nothing wrong with the 2300,it was one of the most widely used and reliable carburetors ever made. IH even used it on medium duty trucks not just light trucks and Scouts. They are one of the easiest to rebuild.matter of fact it was the first type I ever did. It took an afternoon from removal to reinstall and adjust. Badda Bing done!

I didn't see anyone mention a couple very simple checks to make... Relating to the "howling" I've had both of these happen, the carb. was "loose" on the base gasket,tightened them and problem solved. The 2nd was from oversight,forgot to put the gasket back between the air cleaner and carb. and that made a whistling sound.Air like water and electricity seek the path of least resistance and can make all kinds of sounds.

The hesitation I still believe is the acc. pump and that's from experience,it's one of the most common issues with Holley's that use that type. I sold so many I dug into my grey matter and pulled up the pn (243210R91). If it's not shot,it will be. Since he believes the carb. is a replacement who knows what it was,a reman? Used? How long did the truck sit unused? A lot of things can happen inside a "dry" carb.
It would be wise either way to overhaul it using a quality kit with parts more suitable to today's gas.

It could certainly be something else. Vacuum advance? Which is controlled with a ported vacuum switch on the intake manifold,which could also be bad(?).
There should be 2 PVS' possibly 3 with one (if 3) being on the radiator. The other PVS on the intake manifold is for the EGR system. That's if they are even still there,who knows what the PO might have removed besides changing the air cleaner? If original the distributor is a Holley electronic with the infamous "gold box",btw so no points to cause issues.

If Nadz goes thru everything and still has problems/questions I'm sure he'll ask.From his 2nd post I highly doubt he's looking at anything more than getting the truck running better,especially something like TBI and the it would incur. If he wants to look into such a thing at some point,I believe one or two of the light line parts vendors has a kit for it.

I think you missed the point of the 500 CFM. The 2300 is a good carb, but needs to be sized correctly to get the most from it. 500 on the 304 is never going to give the best results, better to find a correct carb than to try and work with the 500 unless you are very experianced in carb work.