Magnum heads on a 74' 318 LA
The crosswind intake is less then an airgap but the same design and drilled for both style heads out of the box, it also has the bosses for injectors if you wanted to go that route. If just looking for simple and low cost just keep the heads stock, heck you can find low mile used ones that will be great. A mild cam, the lifters and pushrods, the crosswind and headers and you will be pretty happy with the motor. Should be as good as a stock 340.