You can certainly squeeze some horses out of 326. But be careful of a couple of things... 1st as mentioned if the compression ratios are too high the car becomes a PITA. Tuning is finicky and needs fancy gas. Also beware of over carbing it. The next thought is if you keep it "original" you will be putting a lot of time and money into the 326. And after all those mods is it "original" anymore? Everyone has a different opinion... and only your opinion matters because it's your car. That being said you can easily drop a stockish 400 in there and your peppy cruiser will be a no brainer. You will hear that quite a bit. And it makes sense and doesn't cost any more. Last thought... with the small cube Pontiacs, or any lower cube muscle car for that matter, gearing is very important if you want to move out.