Lyle, the stock heads you have on that motor are pretty decent ones, especially if your goal is street performance and torque. They should have the 1.94/1.50 valves I suggest you go for the old fashioned hot rodder tricks such as headers, ignition, cam, manifold and carb, along with performance pipes and mufflers. If you really want to mess with heads, I would suggest just a mild port job to blue print them and match them out to the gaskets. Have hardened seats put in for the unleaded gas. Those changes would definitely change the seat of the pants feel of your car. Some of the performance companies like Edelbrock and Holley have a whole series of matched combinations. Call them up and tell them exactly what you want to achieve, be sure to tell them the vehicle weight, transmission, gear ratio and how you plan to use it so they can make the best recommendations for you. Those matched combos that are engineered to work together are really a great way to go. If you want to get exotic, maybe one of the aftermarket fuel injection systems would be something to think about.

What car is that motor in? Good luck with it

Pat