Don't sound so discouraged. The 326CI is small, but still has potential.
The standard 326 vs 326 HO shows that the 326 has 8.6 compression and the HO has 10.5 compression.
For now, let's disregard the cubic inch differences between 326 & 389, and the compression differences of the standard vs HO engines.
Both 326CI engines use the same "441" cam. Intake duration: 269 degrees. Ex duration 277 degrees. Intake lift .374". Ex lift .406". Overlap 47 degrees.
So here is the good news. Most Pontiac street cams used the .406" lift, but changed the duration number - along with opening & closing degrees of the intake/exhaust lobes. Note the "441" cam has the .406" lift exhaust so your intakes should be able to take the same lift.
The '64 389CI used the "009" cam - Int/Ex duration: 273/289 Int/Ex Lift: .406" Overlap 54 degrees. The heads used press-in studs. But notice a little more duration on the Int/Ex but the same lift - which is not a real big increase.
What you want to look at is the Overlap. 47 degrees is pretty mild. 54 degrees is a better number for performance. More overlap means a more aggressive cam and typically means a higher RPM power range - and more overlap gives the engine that rough rumpty-rump sound all us motorheads like. As example, the Ram Air IV cam has 87 degrees of overlap and in a 400CI engine it is not a good candidate for low RPM street cruising and really likes to spin 6,000 RPM's.
As the cams got "bigger", heavier valve springs were needed and your HiPerf engines used the bottle-neck 7/16" screw-in rocker arm studs. So if you don't go crazy on a cam - which you probably won't anyway with a 326CI - you should be OK with the factory oil through studs if you plan to keep them.
That said, don't let the 8.6 compression give you much concern. An 8.6 compression engine CAN make power. The trick is, like all engines, to select the correct cam for your engine application.
Pontiac, in general, used what is called a wide lobe separation angle (LSA) near 114 degrees. This provided a nice broad power/torque curve across the engine's RPM range providing good vacuum for accessories, smooth idle, good pull at lower RPM's and nice power as RPM's increase. But of course this was typically with the 10.5 compression of the day.
With the lower 8.6 compression, you want to tighten this up to build more cylinder pressure or Dynamic compression as it is called. Here is where (in my opinion, bigD
) I would recommend a Competition Cams camshaft having a 110 LSA. This will take advantage of your lower 8.6 compression. The 110 LSA will build cylinder pressure and the engine will respond as if you added more compression by changing out to higher compression pistons. The power/torque will be much improved and pull real hard up to a plateau at which it will then drop off like a stone - but I can't tell you what that RPM limit is. An 8.2 400CI I used a Competition Cams 110 LSA in pulled like a freight train and dropped off about 5500-5600 RPM's and you could feel that there was no power to be had revving it any higher.
Now my car had manual drum brakes and no power robbing accessories so low intake vacuum was never an issue and/or something I ever measured. I don't think 110LSA would pose any problems. You might also consider a 112 LSA cam which would most likely give a little more manifold vacuum, but I would still look into the 110 LSA cams first.
So, my recommendation would be to email or contact Competition Cams, Butler Performance, KRE, TinIndian, or anyone else who specializes in Pontiac engine cams/builds and get their recommendation on a kit that includes a matched cam/lifters/springs for your engine.
You should have no problem adding a 4Bbl intake/carb. The original carbs are about 500CFM's which is not very big per say, but just what you will want for the smaller 326CI.