Howdy Back Jake and all:
While there is nothing wrong with the three modifications you listed, without a more comprehensive plan, you will end up with a small increase in power for a big chunk of cash. The 10% increase Rocklord suggested would be based on a good running, well tuned engine. For the same money, roughly $800, you'd be far better off investing in a top end rebuild that includes increasing the compression and flow. Then adding improved intake, exhaust and ignition would really make a difference. The only piece missing, at that point, would be an upgraded cam.
FYI- while the PetroniX Ignitor is a good upgrade, eliminating points and giving a more exact and reliable spark, it will not improve performance, but it will allow a larger spark plug gap. That along with increasing the initial advance setting will. Add a hotter coil and better spark plug wires is also worthwhile.
FYI- a header exhaust will make the biggest difference at higher rpms. With a stock cam and compression your engine will be peaking out well below 5,000. A header for our engines is one of the most expensive upgrades. Without a complete package, it's not very cost effective.
The two stage two barrel through an adapter does make some sense. Well tuned, it can give slightly better economy and slightly more power. Read, "Well Tuned". Tuning these carbs is an art. That along with adapting linkage and loss of hood clearance makes this mod a bit of a challenge.
If you are looking for cost effective upgrades consider; performance tune-up optimizing ignition and carb. If you are committed to your stock ignition, a PetronX Ignitor is a good, foundational addition along with a hotter coil. But, before spending a dime plan on what you might want to do in the future. FYI, your carb and ignition need to be compatible; SCV type carb to a Load-O-Matic distributor, or ported vacuum source to a vacuum advance ignition. If you plan to upgrade either carb or ignition in the future, you might want to save your money until you have a plan.
Sorry if we are raining on your parade, but better to know now. Keep thinking and keep the questions coming.
Adios, David
