The stroker kit is from 440 source. Of course you know where the heads are from. I am not looking to build a race car, but just a strong street rider. I knew the heads out of the box would need to be opened up , but Kurt seemed to think they would do Ok with a really good port job. He built a few motors with these heads, but not sure if he did a 543. Thanks for the info. I will look into it!! Matt B.