This means you will need heads with stock sized exhaust ports (not Stage II). Your choices would be Edelbrock, TA or stock heads.
I thought the potential of the Stage II heads would be wasted in your application. The other heads listed in this post would be fine for you, but with the smaller valves (non Stage-One valves). The Stage-One valves will fit within your 430 engine bore, but may actually cause a preformance loss. TA recommends the smaller valves for the 400 in both the stage one and stage II heads on their website, and I have seen articles in my GS-X-Tra over the years that the stage one valves will be shrouded by the 430 bore and provide less performance (unrestricted air flow) then the smaller valve in the same engine.
There will not be a great performance difference in your application between aftermarket aluminum stock castings with small valves or your existing heads ported with the same small valves. That is why your current heads with porting and without hardened seats was suggested as the most bang for the buck. You could have them checked for cracks locally before sending them off.
The stock exhaust manifolds end in a much smaller diameter then any 2.5" exhaust system you pick, and they are restrictive inside as well. The exhaust diameters of 2.5" is about as small as you want to go in a performance big block Buick build. Headers usually end in a 3"-3.5" collector that is reduced down to 2.5"-3" exhaust system. More horsepower needs to move more air without restriction. The stock manifolds are great at stock levels, but are restrictive as horsepower and RPMs go up. Porting them reduces some restriction and equalizes flow to some degree. Ported manifolds will never be able to flow or equalize flow as much as headers, but they are a step in the right direction.
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