The stock heads will work just fine, unless you are planning on going to the track you don't need to update your cam either. New intake and 4v carb will give you a nice strong cruiser. You don't need to upgrade the radiator / fan either, the car isn't going to be running any hotter for what you are doing to it. Hell if anything it will cool better.

If you plan on staying with the cast iron heads I would seriously consider having them upgraded, if you will be driving the car quite a bit.
Hardened valve seats and screw in rocker studs , might even need new valve guides.
For the difference in money I opted for aluminum heads rather than the above route.
Your mileage may vary.

Hi Jonathan!!

I also bought a 68 with the basic 190HP 289 and 2v carb a few years ago and like you I just wanted to have more fun with the engine on a budget. A new carburetor and intake is an easy fix and exactly what I started with. Just the difference in weight between the stock intake and a new aluminum one is worth it even if you dont get a single hp :P

Not sure how much HP are gained from these 2 upgrades though...as I found out my engine was ready to die when I opened it up for the swap and had to build a new one. :( Heads are expensive but make a big difference in HP. Modern aluminum ones will also be more suited for modern gasoline where cast iron one tend to wear out faster. I think Im around 340 HP now, and I stil havent had to change the stock 1" radiator. I drive on the streets only, no racing, I do push it from time to time but even on a hot day, it still doesnt overheat. This said, it WILL be my next purchase just to be on the safe side. :) Hope this helps. Im still a noob at this but happy to help when I can.

I had a 65 289 4 barrel with positraction. Learned the hard way that if you punched it hard you could get wheel hop and tear up the positraction. If you never punch it hard from stop you probably don't have to worry..
Bill