318 heads

That sounds like a solid recommendation. It appears that would even be significantly cheaper than machining the heads you have and could/should give a bump in compression as well. They would be a direct bolt on vs. the Magnum stuff which would require additional modifications and parts.

Many on here will caution you against going with a 340/360 LA head due to the lower compression (which the typical 318 can't afford to lose).

Is your car running the original 318?