It depends on which Holley carb you have, the front bowl can have 2 different fuel inlets, the one that works with the 4.3 is the bowl with the side fuel inlet, not the inlet that is on the front of the bowl....
front inlet:
All Holley Marine Carburetors are designed to meet Coast Guard specifications. A marine carburetors fuel metering system is calibrated to compensate for unique engine loads found on boats. The J-style vent tubes direct fuel/fumes back into the carburetor for safe operation while on rough...
www.holley.com
side inlet:
All Holley Marine Carburetors are designed to meet Coast Guard specifications. A marine carburetors fuel metering system is calibrated to compensate for unique engine loads found on boats. The J-style vent tubes direct fuel/fumes back into the carburetor for safe operation while on rough...
www.holley.com
Holley actually sells a 4160 4bbl that was jetted and set up for the 4.3 V6s:
All Holley Marine Carburetors are designed to meet Coast Guard specifications. A marine carburetors fuel metering system is calibrated to compensate for unique engine loads found on boats. The J-style vent tubes direct fuel/fumes back into the carburetor for safe operation while on rough...
www.holley.com
It's amazing how expensive these have gotten, I paid about $300 less than the price listed here, 5 years ago.
Not sure if you can change the front bowl to a side inlet style, you might call Holley tech support & ask them.
The last one I posted for sure fits the 4.3 V6 just fine, you do have to use an adapter due to using a square bore 4bbl on a spread bore manifold but it fits.
Personally I think the original Quadrajet is a superior carb. I tried the Holley, it just wouldn't run right and went back to the Q-jet.