Bottom line is........the budget. Anyone here can suggest a ton of add-on parts right down to a complete crate engine.
From what I have read, it seems you want to get your best bang for the buck and keep it basic & simple. About right?
So go with what most of us did with any car "back in the day." Add a better exhaust system as you will not benefit any engine add-ons if the exhaust won't flow. Dual exhaust with a larger sized pipes and free flowing mufflers would be a minimum and factory type cast iron HP manifolds or headers of any type are always preferred, but headers can lead to fitment problems needing to be overcome with the big hammer technique - which by the way has been proven to affect nothing in loss of HP, so hammer away. So my first improvement would be the exhaust system.
Then the intake system would be next on my list. This would include the carb, intake, and air cleaner assembly. You want what is called a "dual plane" intake for the street. Provides good manners for all kinds of driving and maintains a high port velocity for good throttle response at all RPM's. Typically will work from idle on up to 5-5,500 RPM's. Stay away from the "single plane" intakes unless you have an engine that can take advantage of them which is typically a higher RPM engine.
The Edlebrock Performer might be a better bet over the RPM Performer which has a taller mounting at the carb to enhance higher RPM's. BUT, as you stated, won't work with your AC. That said, you can "clean up" your stock 4Bbl intake by gasket matching the ports and smoothing out any rough casting lines or bumps that are accessible with a high speed die grinder and carbide cutter. This will
increase air flow and this is what you want for more FREE HP.
You can also experiment with a carb spacer to add more HP. The "dual plane" manifold splits the carb, the left front/rear barrels feed one side of the engine while the right barrels feed the other. Raise the carb up with an open spacer, each side of the engine now feed off of all 4 barrels - the left and the right, in effect giving you a larger carburetor without getting one. This works providing you have the needed clearance between hood and top of air cleaner or get a low profile air cleaner to make the necessary clearance.
Personally, I think a 600CFM carb is too small for a 383. I would want a 650CFM as a minimum, but really go with a 750CFM having the vacuum secondaries (if it will fit your manifold base as some are "square port" while a 750 carb has slightly larger secondary bores. Some manifolds can be opened up to match if enough material is available). Vacuum secondaries compensates the engine in that they only open as the engine needs the extra air/fuel. It creates a smoother and better transition on a basic street engine. If too big, the secondaries are only going to open enough as needed, but no doubt as RPM's build in the 383, the carb will keep up and provide the power needed. Too small a carb can starve the engine, so higher RPM's or better flowing intake will be a waste as it can peak earlier than the potential of the engine's power band.
I would get the largest and most unrestrictive air cleaner I could install. More air is more power. Get a spare factory air cleaner if you have to have it, and drill evenly spaced 1" holes all around the outside perimeter to allow for more air flow. Tell people it was a Nascar option. LOL
Your 9.2 compression with iron heads is about the most you want for a street engine with iron heads if using pump gas. As you start to hit 9.5, you begin to need higher octane gas through additives or racing gas. This means you want to be very careful with cam selection IF you choose to install a new cam grind. Their are many things involved when selecting a "street" cam. You don't want one that will capture/build more cylinder pressure and effectively raise your 9.2 compression even higher. So an engine having 8.4, 9.2, or 10.0 compression would each require a different matching grind for street performance. There are many factors that go into a good choice and it is best not to rely on the recommendations of others, but let a cam grinder/manufacturer suggest a cam for your specific application. Choose the wrong cam, and the engine could be a slug nor match all the improvements you have made to the engine. The cam, in my opinion, it the most important piece in the engine and then you can build around it once you know what you want your engine/car to do.
I would also add to this list 2500 RPM stall converter. I would get what is called a "tight" converter, one that has little slip when using light/part throttle and comes on strong when you nail the gas. I used a company called Edge Racing Converters (
727 : Edge Racing Converters, More Horsepower with More Torque Guaranteed! ) for my brother's 904 transmission behind a 360CI SixPack engine. It worked as claimed. I have a factory 2500 RPM converter behind my 360CI and it slips a whole lot more and I would go with one of these converters to replace it in an instant and probably will when I rebuild the trans at some point. This will also improve performance, especially at a stop light take-off under full throttle.
